2.1.1 Outline the cell theory The cell theory states that: 1. All living things are composed of cells (or cell products) 2. The cell is the smallest unit of life 3. Cells only arise from pre-eisting cells
2.1.2 Discuss the evidence for the cell theory Microscopes: !icroscopes have increased man"s a#ility to visualise tiny o#$ects All living living things %hen vie%ed vie%ed under a microscope microscope have have #een found found to #e #e made of cells and cell products (e.g. hair) Note: Certain types of cells do not conform to the standard notion of %hat constitutes a cell !uscle cells contain multiple nuclei &ungal hyphae consist of multiple cells that share a continuous cytoplasm
'ight vs lectron !icroscopes
Experimental Evidence: Cells removed from tissues can survive independently for short periods of time othing smaller than a cell has #een found to #e a#le to live independently periments #y &rancesco *edi and 'ouis +asteur have demonstrated that cells cannot gro% in sealed and sterile conditions
,istory of the Cell Theory 2.1.3 State that unicellular unicellular organisms carry out all the the functions of life life nicellular organisms (such as amoe#a paramecium euglena and #acterium) are the smallest organisms capa#le of independent life. All living things share share / #asic #asic characteristi characteristics: cs:
sho% movement either eternally or internally ovement: 'iving things sho% eproduction: 'iving things produce offspring either seually or aseually ensitivity: 'iving things can respond to and interact %ith the environment
gro% or change si0e shape rowth: 'iving things can gro% espiration: 'iving things use su#stances from the environment to mae energy xcretion: 'iving things ehi#it the removal of %astes
echange materials and gases %ith the utrition: 'iving things echange environment 2.1.4 Compare the relative relative sizes of molecules, cell memrane thic!ness, viruses, acteria, organelles and cells, using appropriate S" units Relative sizes:
Unit Conversion Ta Table: ble:
A molecule 1 nm Cell mem#rane thicness /.4 nm 5irus 166 nm (range: 26 - 266 nm) 7acteria 1 - 4 um 8rganelles 916 um uaryotic cells 9166 um iagram of the *elative ;i0es and ;cale of 7iological !aterials
Cell ;i0e and ;cale ('earn
To calculate the linear magnification of a dra%ing the follo%ing e=uation should #e used: Magni fi cat i on=Si z eofi mage( wi t hr ul er )÷Ac t ual s i z eofobj ec t
( ac cor di ngt os cal ebar )
T oc al c ul at et heac t ual s i z eofamagni fi eds pec i ment heequat i oni ss i mpl yr ea r r a n g e d : Ac t ual s i z e=Si z eofi mage( wi t hr ul er )> !agnification 2.1.% &'plain the importance of the surface area to volume volume ratio as a factor factor limiting cell size The rate of meta#olism of a cell is a function of its mass volume The rate of material echange in and out of a cell is a function of its surface area As the cell cell gro%s gro%s volume increas increases es faster than surface surface area area (leading (leading to a decreased ;A:5ol ratio) ?f the meta#olic rate is greater than the rate of echange of vital materials and %astes the cell %ill eventually die ,ence the cell must conse=uently divide in order to restore a via#le ;A:5ol ratio and survive Cells and tissues specialised for gas or material echange (e.g. alveoli) %ill increase their surface area to optimise the transfer of materials
!icrovilli increase surface area allo%ing for a more efficient echange of materials heat
2.1.( State that multicellular organisms sho$ emergent properties mergent properties arise from the interaction of component parts: the %hole is greater than the sum of its parts !ulticellular organisms are capa#le of completing functions that individual cells could not undertae - this is due to the interaction #et%een cells producing ne% functions ?n multicellular organisms: Cells may group together to form tissues 8rgans are then formed from the functional grouping of multiple tissues 8rgans that interact may form organ systems capa#le of carrying out specific #ody functions 8rgan systems carry out the life functions re=uired #y an organism
'evels of Anatomical 8rganisation
2.1.) &'plain that cells in multicellular organisms differentiate to carry out specialised functions y e'pressing some of their genes and not others
All cells of an individual organisms share an identical genome - each cell contains the entire set of genetic instructions for that organism The activation of different instructions (genes) %ithin a given cell #y chemical signals %ill cause it to differentiate from other cells lie it ifferentiation is the process during development %here#y ne%ly formed cells #ecome more specialised and distinct from one another as they mature Active genes are usually pacaged in an epanded and accessi#le form (euchromatin) %hile inactive genes are mainly pacaged in a condensed form (heterochromatin)
ifferentiated cells %ill have different regions of A pacaged as heterochromatin and euchromatin depending on their function ifferential
2.1.* State that stem cells retain the capacity to divide and have the aility to differentiate along different path$ays ;tem cells are unspecialised cells that have t%o ey =ualities: 1. Sel renewal: They can continuously divide and replicate 2. !otency: They have the capacity to differentiate into specialised cell types
;tem Cells
2.1.1+ Outline one therapeutic use of stem cells ;tem cells can #e derived from em#ryos or the placenta um#ilical cord of the mother@ also minimal amounts can #e harvested from some adult tissue ;tem cells can #e used to replace damaged or diseased cells %ith healthy functioning ones This process re=uires: The use of #iochemical solutions to trigger differentiation into desired cell type ;urgical implantation of cells into patient"s o%n tissue ;uppression of host immune system to prevent re$ection of cells Careful monitoring of ne% cells to ensure they do not #ecome cancerous
amples of therapeutic uses of stem cells: 1. Retinal cells: *eplace dead cells in retina to cure diseases lie glaucoma and macular degeneration 2. S"in cells:
2.2.2 nnotate the diagram $ith the function of each of the named structures Cell 'all: A rigid outer layer made of peptidoglycan that maintains shape and protects the cell from damage or #ursting if internal pressure is high Cell Membrane: ;emi-permea#le #arrier that controls the entry and eit of su#stances Cytoplasm: &luid component %hich contains the en0ymes needed for all meta#olic reactions Nucleoid: *egion of the cytoplasm %hich contains the genophore (the proaryotic A)
!lasmid: Additional A molecule that can eist and replicate independently of the genophore - it can #e transmitted #et%een #acterial species Ribosome: Complees of *A and protein that are responsi#le for polypeptide synthesis (proaryotic ri#osomes are smaller than euaryotes - /6;) Slime Capsule: A thic polysaccharide layer used for protection against dessication (drying out) and phagocytosis (la)ella *sin)ular la)ellum+: 'ong slender pro$ection containing a motor protein %hich spins the flagella lie a propellor ena#ling movement !ili *sin)ular pilus+: ,air-lie etensions found on #acteria %hich can serve one of t%o roles ,ttachment pili: ;horter in length they allo% #acteria to adhere to one another or to availa#le surfaces Sex pili: 'onger in length they allo% for the echange of genetic material (plasmids) via a process called #acterial con$ugation 2.2.3 "dentify structures from 2.2.1 in electron micrographs of &. coli lectron !icrograph of &scherichia coli
2.2.4 State that acterial cells divide y inary fission 7inary fission is a form of aseual reproduction and cell division used #y proaryotic organisms ?t is not the same as mitosis there is no condensation of genetic material and no spindle formation ?n the process of #inary fission: The circular A is copied in response to a replication signal The t%o A loops attach to the mem#rane The mem#rane elongates and pinches off (cytoinesis) forming t%o separate cells
The +rocess of 7inary &ission
2.3.1 Dra$ and lael a diagram of the ultrastructure of a liver cell as an e'ample of an animal cell $% Representation &% Representation
2.3.2 nnotate the diagram from 2.3.1 $ith the functions of each named structure Cell Membrane: ;emi-permea#le #arrier that controls the entry and eit of su#stances Cytosol: The fluid portion of the cytoplasm (does not include the organelles or other insolu#le materials)
Nucleus: Contains hereditary material (A) and thus controls cell activities (via transcription) and mitosis (via A replication) Nucleolus: ;ite of the production and assem#ly of ri#osome components Ribosome: Complees of *A and protein that are responsi#le for polypeptide synthesis (euaryotic ri#osomes are larger than proaryotes - B6;) Mitochondria: ;ite of aero#ic respiration %hich produces large =uantities of chemical energy (AT+) from organic compounds -ol)i ,pparatus: An assem#ly of vesicles and folded mem#ranes involved in the sorting storing and modification of secretory products .ysosome: ;ite of hydrolysis digestion #reado%n of macromolecules !eroxisome: Catalyses #read%on of toic su#stances lie hydrogen peroide and other meta#olites Centrioles: !icrotu#ule-organising centres involved in cell division (mitosis meiosis and cytoinesis) Endoplasmic Reticulum: A system of mem#ranes involved in the transport of materials #et%een organelles Rou)h ER: ;tudded %ith ri#osomes and involved in the synthesis and transport of proteins destined for secretion Smooth ER: ?nvolved in the synthesis and transport of lipids and steroids as %ell as meta#olism of car#ohydrates 2.3.3 "dentify the structures in 2.2.1 in electron micrographs of a liver cell lectron !icrograph of a 'iver Cell
2.3.4 Compare pro!aryote and eu!aryote cells Similarities: 7oth have a cell mem#rane 7oth contain ri#osomes
7oth have A and cytoplasm %ierences:
2.3.# State three differences et$een plant and animal cells 'a#elled iagram of a
2.3.% Outline t$o roles of e'tracellular components !lants The cell %all in plants is made from cellulose secreted from the cell %hich serves the follo%ing functions: +rovides support and mechanical strength for the cell (maintains cell shape) +revents ecessive %ater uptae #y maintaining a sta#le turgid state ;erves as a #arrier against infection #y pathogens ,nimals The etracellular matri (C!) is made from glycoproteins secreted from the cell %hich serve the follo%ing functions: +rovides support and anchorage for cells ;egregates tissues from one another *egulates intercellular communication #y se=uestering gro%th factors 2.4.1 Dra$ and lael a diagram to sho$ the structure of memranes
2.4.2 &'plain ho$ the hydrophilic and hydrophoic properties of phospholipids help to maintain the structure of cell memranes Structure o !hospholipids Consist of a polar head (hydrophilic) made from glycerol and phosphate Consist of t%o non-polar fatty acid tails (hydropho#ic) ,rran)ement in Membrane +hospholipids spontaneously arrange in a #ilayer ,ydropho#ic tail regions face in%ards and are shielded from the surrounding polar fluid %hile the t%o hydrophilic head regions associate %ith the cytosolic and etracellular environments respectively Structural !roperties o !hospholipid #ilayer +hospholipids are held together in a #ilayer #y hydropho#ic interactions (%ea associations) ,ydrophilic hydropho#ic layers restrict entry and eit of su#stances +hospholipids allo% for mem#rane fluidity flei#ility (important for functionality) +hospholipids %ith short or unsaturated fatty acids are more fluid +hospholipids can move hori0ontally or occasionally laterally to increase fluidity &luidity allo%s for the #reaing remaing of mem#ranes (eocytosis endocytosis) 2.4.3 /ist the functions of memrane proteins
ransport: +rotein channels (facilitated) and protein pumps (active) eceptors: +eptide-#ased hormones (insulin glucagon etc.) nchora)e: Cytoseleton attachments and etracellular matri ell reco)nition: !,C proteins and antigens ntercellular /oinin)s: Tight $unctions and plasmodesmata nzymatic activity: !eta#olic path%ays (e.g. electron transport chain) 2.4.4 Define diffusion and osmosis %iusion: The net movement of particles from a region of high concentration to a region of lo% concentration (along the gradient) until e=uili#rium 0smosis: The net movement of %ater molecules across a semi-permea#le mem#rane from a region of lo$ solute concentration to a region of high solute concentration until e=uili#rium is reached
8smosis 2.4.# &'plain passive transport across memranes in terms of simple diffusion and facilitated diffusion
The plasma mem#rane is semi-permea#le and selective in %hat can cross ;u#stances that move along the concentration gradient (high to lo%) undergo passive transport and do not re=uire the ependiture of energy (AT+)
Simple diusion: ;mall non-polar (lipophilic) molecules can freely diffuse across the mem#rane
(acilitated diusion: 'arger polar su#stances (ions macromolecules) cannot freely diffuse and re=uire the assistance of transport proteins (carrier proteins and channel proteins) to facilitate their movement (facilitated diffusion) 2.4.% &'plain the role of protein pumps and 0 0 in active transport across memranes Ac t i v et r ans por ti st hepas sageofmat er i al sagai ns tac onc ent r at i on
gr adi ent( f r om l owt ohi gh) Thi spr oc es sr equi r est heus eofpr ot ei npumpswhi c hus et heener gyf r om ATPt ot r ans l oc at et hemol ec ul esagai ns tt hegr adi ent Theh ydr ol y s i sofATPc aus esac onf or mat i onal c ha ngei nt hepr ot ei n pumpr es ul t i ngi nt hef or c edmo mo v ementoft hesubs t anc e
Pr o t ei npumpsar es pec i fi cf oragi v enmol ec ul e,al l o wi ngf ormo v ementt o ber egul at ed( e. g.t omai nt ai nc hemi c al orel ec t r i c al gr adi ent s ) Anex a mp mp l eo fa nac t i v et r an s por tme c ha ni s mi st h eN / a+K+ pumpwhi chi s i nv ol v edi nt hegener at i onofner v ei mpul s es TypesofMemb mbr aneTr anspor t
2. 4. 7 Ex pl ai nhowv es i c l esar eus edt ot r ans por tmat er i al swi t hi nac el l bet ween t heend op l a s mi mi cr e t i c u l u m,Go m, l g iap par a t usa ndpl a s mame ma me mb mb r a ne
Pol y pept i desdes t i nedf ors ec r et i onc ont ai nani ni t i al t ar gets equenc e( a s i gnal r ec ogni t i onpept i de)whi c hdi r ec t st her i bos omet ot heendopl as mi mi c r et i c ul um Thepol y pept i dec ont i nuest obesy nt hes i s edbyt her i bos omei nt ot he l umeno ft heER,wh er et hes i g na ls eq uen c ei sr e mo mo v edf r o mt h en as c e ntc h ai n Thepol y pept i dewi t hi nt her oughERi st r ans f er r edt ot hegol gi appar at us v i aav e si c l e,whi c hf or msf r om t heb udd i ngoft heme membr an e Thepol y pept i demov esv i av es i c l esf r om t hec i sf ac eoft hegol gi t ot he t r ansf ac eandma ybemodi fi edal ongt hewa y( e. g.gl y c os y l at ed,t r unc at ed,et c . ) Thepol y pept i dei sfi nal l yt r ans f er r edv i aav es i c l et ot hepl as ma ma membr ane,wher ebyi ti sei t heri mmedi at el yr el eas ed( c ons t i t ut i v es ec r et i on)or s t or edf oradel ay edr el eas ei nr es pons et os omec el l ul ars i gnal ( r egul at or y s ec r e t i on=f oramo mor econc ent r at edan dmor esus t ai ne deff ec t ) Ov er v i e w ofVes i c ul arT r ans por t
2. 4. 8 Des c r i behowt hefl ui di t yoft hemembr aneal l owsi tt oc hanges hape, br eakandr ef or m dur i ngend oc y t os i sande x oc y t os i s Themembr anei spr i nc i pal l yhel dt oget herb yt her el at i v el yweakhy dr ophobi c as s oc i at i onsb et weenphos phol i pi ds Thi sas soc i at i onal l owsf ormembr anefl ui di t yandfl ex i bi l i t y ,ast hephos phol i pi ds ( andt oal es s ere x t entt hepr o t ei ns )c anmo v ea boutt os omee x t ent
Thi sal l owsf ort hebr eak i ngandr emak i ngofmembr anes ,al l owi ngl ar ger s ubs t anc esac ces si nt oandoutoft hec el l ( t hi si sanac t i v epr oc es s)
Endocyt osi s
Thepr oc es sbywhi c hl ar ges ubs t anc es( orbul kamount sofs ma l l er s ubs t anc es )ent ert hec el l wi t houtt r av el l i ngac r os st hepl as mamembr ane Ani n v agi nat i onoft hemembr anef or msafl as k l i k edepr es s i o nwhi c h env el opest hemat er i al ;t hei nv agi nat i oni st hens eal edofff or mi ngav es i c l e Th er ear et woma i nt y pe sofe nd oc y t os i s : 1.Phagoc y t os i s Thepr oc es sbywhi c hs ol i ds ubs t anc es( e. g.f oodpar t i c l es ,f or ei gn pat hogens )ar ei nges t ed( us ual l yt obet r ans por t edt ot hel y s os omef orbr eak do wn) 2.Pi noc yt os i s Thepr oc es sbywhi c hl i qui ds/s ol ut i ons( e. g.di s sol v eds ubs t anc es )ar e i nges t edbyt hec el l ( al l owsqui c kent r yf orl ar geamount sofs ubs t anc e) Ex oc yt os i s
Thepr oc es sbywhi c hl ar ges ubs t anc esex i tt hec el l wi t houtt r av el l i ng acr osst hepl asmamembr ane Ves i c l es( us ual l yder i v edf r om t hegol gi )f us ewi t ht hepl as mamembr ane ex pel l i ngt hei rc ont ent si nt ot heex t r ac el l ul arenv i r onment Th ePr o c es sofEx o c y t o si s
2.#.1 Outline the stages in the cell cycle, including interphase 1, S, 2 -, mitosis and cyto!inesis The cell cycle is an ordered set of events that culminates in cell gro%th and division into t%o daughter cells ?t can roughly #e divided into t%o main stages: 1nterphase The stage in the development of the cell #et%een t%o successive ! phases This phase of the cell cycle is a continuum of 3 distinct stages (< 1 ; <2) %here#y the cell gro%s and matures (< 1) copies its A (;) and prepares for division (<2) ;ometimes cells %ill leave the cell cycle and enter into a =uiescent state (<6) %here#y it #ecomes amitotic and no longer divides M phase The periods of nuclear division (mitosis) and cytoplasmic division (cytoinesis)
The Cell Cycle ! +hase
2.#.2 State that tumours cancers- are the result of uncontrolled cell division and that these can occur in any organ or tissue The cell cycle is controlled #y a comple chemical control system that responds to signals #oth inside and outside of the cell Tumor suppressor genes produce proteins %hich inhi#it cell division %hile proto-oncogenes produce proteins that promote gro%th and division !utations to these genes result in uncontrolled cell division resulting in the formation of a tumour Tumours can gro% in si0e %hich causes damage local tissue@ they may also spread to other parts of the #ody (malignant tumours) iseases caused #y the gro%th of tumours are collectively no%n as cancers
Cancer in Tasmanian evils 2.#.3 State that interphase is an active period in the life of a cell $hen many metaolic reactions occur, including protein synthesis, D replication and an increase in the numer of mitochondria and chloroplasts ?nterphase is an active period in the life of a cell - many events need to occur #efore a cell can successfully undergo division:
rotein synthesis: The cell needs to synthesise ey proteins and en0ymes to ena#le it to gro% copy its contents and then divide
T! production: The cell %ill need to generate sufficient =uantities of AT+ in order to successfully divide
ncrease number o or)anelles: The cell needs to ensure #oth daughter cells %ill have the necessary num#ers of organelles needed to survive N, replication: The genetic material must #e faithfully duplicated #efore division (this occurs during the ; phase)
As none of these processes can occur during the ! phase interphase contains gro%th checpoints to ensure division is via#le A checpoint stage #efore A replication during %hich the cell gro%s duplicates organelles synthesises proteins and produces AT+ The stage during %hich A is replicated A checpoint stage #efore division during %hich the copied A is checed for fidelity (mutations) and final meta#olic reactions occur 2.#.4 Descrie the events that occur in the four phases of mitosis
!rophase A supercoils causing chromosomes to condense and #ecome visi#le under a light microscope As A %as replicated during interphase the chromosomes are each comprised of t%o genetically identical sister chromatids $oined at a centromere The centrosomes move to opposite poles of the cell and spindle fi#res #egin to form #et%een them (in animals each centrosome contains 2 centrioles) The nuclear mem#rane is #roen do%n and disappears Metaphase ;pindle fi#res from the t%o centrosomes attach to the centromere of each chromosome Contraction of the microtu#ule spindle fi#res cause the chromosomes to line up separately along the centre of the cell (e=uatorial plane) ,naphase
Continued contraction of the spindle fi#res cause the t%o sister chromatids to separate and move to the opposite poles of the cell 8nce the t%o chromatids in a single chromosome separate each constitutes a chromosome in its o%n right Telophase 8nce the t%o sets of identical chromosomes arrive at the poles the spindle fi#res dissolve and a ne% nuclear mem#rane reforms around each set of chromosomes The chromosomes decondense and are no longer visi#le under a light microscope The division of the cell into t%o daughter cells ( cyto!inesis) occurs concurrently %ith telophase 2.#.# &'plain ho$ mitosis produces t$o genetically identical nuclei
uring interphase (the ; phase) the A %as replicated to produce t%o copies of genetic material These t%o identical A molecules are identified as sister chromatids and are held together #y a single centromere uring the events of mitosis (as descri#ed in 2.4.) the sister chromatids are separated and dra%n to opposite poles of the cell hen the cell divides (cytoinesis) the t%o resulting nuclei %ill each contain one of each chromatid pair and thus #e genetically identical 2.#.% State that gro$th, emryonic development, tissue repair and ase'ual reproduction involve mitosis rowth: !ulticellular organisms increase their si0e #y increasing their num#er of cells through mitosis sexual reproduction: Certain euaryotic organisms may reproduce aseually #y mitosis (e.g. vegetative reproduction)
issue Repair: amaged tissue can recover #y replacing dead or damaged cells mbryonic development: A fertilised egg (0ygote) %ill undergo mitosis and differentiation in order to develop into an em#ryo 3.1.1 State that the most freuently occurring chemical elements in living things are caron, hydrogen, o'ygen and nitrogen The approimate proportions of the four main elements in living things are: D Car#on (1EF) D ,ydrogen (16F) D 8ygen (G4F) D itrogen (3F) 3.1.2 State that a variety of other elements are needed y living organisms, including sulphur, calcium, phosphorus, iron and sodium 8utside of the four main elements living things may contain trace amounts of 26 or so other elements including: D ;ulphur (6.24F) D Calcium (1.4F) D +hosphorus (1F) D ?ron (6./F) D ;odium (6.14F) 3.1.3 State one role for each of the elements mentioned in 3.1.2 Sulphur * +: &ound in certain amino acids (cysteine and methionine) allo%ing proteins to form disulphide #onds Calcium * +: &ound in #ones and teeth also involved in neurotransmitter release in synapses !hosphorus * +: Component of nucleic acids and cell mem#ranes 1ron * +: &ound in haemoglo#in (animals) allo%ing for oygen transport Sodium * +: ?nvolved in the generation of nerve impulses in neurons 3.1.4 Dra$ and lael a diagram sho$ing the structure of $ater molecules to sho$ their polarity and hydrogen ond formation Structure o a 'ater Molecule:
ater (,28) is made up of t%o hydrogen atoms covalently #ound to an oygen atom
hile this #onding involves the sharing of electrons they are not shared e=ually The oygen atom having more protons (Hve) attract the electrons (-ve) more strongly (i.e. the oygen has a higher electronegativity) Thus the oygen atom #ecomes slightly negative and the hydrogen atoms #ecome slightly positive 2ydro)en #ondin) between 'ater Molecules Covalently #onded molecules that have a slight potential charge are said to #e polar The slightly charged regions of the %ater molecule can attract other polar or charged compounds ater molecules can associate via %ea hydrogen #onds (&8 #onding %ith ,)
;tructure and 7onding of ater !olecules
3.1.# Outline the thermal, cohesive and solvent properties of $ater Thermal !roperties ater has a high specific heat capacity (the measure of energy re=uired to
raise the temperature of 1 g of su#stance#y 1 IC)
ater has a high heat of vaporisation (amount of energy a#sor#ed per gram as it changes from a li=uid to a gas vapour) ater has a high heat of fusion (amount of energy re=uired to #e lost to change 1 g of li=uid to 1 g of solid at 6 IC) These properties occur as a result of the etensive hydrogen #onding #et%een %ater molecules - this allo%s %ater to a#sor# considera#le amounts of energy %ith little change in form (,-#onds need to #e #roen first) Cohesive !roperties ater molecules are strongly cohesive (they tend to stic to one another) ater molecules %ill also tend to stic to other molecules that are charged or polar (adhesion) These properties occur as a result of the polarity of a %ater molecule and its a#ility to form hydrogen #onds %ith appropriate molecules Solvent !roperties ater can dissolve many organic and inorganic su#stances that contain electronegative atoms (such as fluorine oygen and nitrogen) This occurs #ecause the polar attraction of large =uantities of %ater molecules can sufficiently %eaen intramolecular forces (such as ionic #onds) and result in the dissociation of the atoms 0ther !roperties ater is transparent allo%ing light to pass through it (important for photosynthesis) ater epands %hen fro0en #ecoming less dense lighter (important for life on earth - oceans don"t free0e) 3.1.% &'plain the relationship et$een the properties of $ater and its use in living organisms as a coolant, medium for metaolic reactions and transport medium Coolant 7oth plants and animals use the evaporation of %ater from the surfaces of their #odies to facilitate cooling (s%eating and panting in animals transpiration from leaves in plants) ater can #e used to carry heat to cooler places in our #odies (countercurrent echange of thermal energy) Medium or Metabolic Reactions ater can dissolve many organic and inorganic su#stances to facilitate chemical reactions ater can also a#sor# thermal energy released as a #y-product of many chemical reactions
Transport Medium The forces of attraction #et%een %ater molecules help facilitate the transport of %ater up the ylem of plants ater is an effective transport medium for dissolved su#stances (in plants minerals from the soil and sugars from the leaves can #e transported in %ater through the ylem and phloem respectively@ %hile in animals %ater in the #lood is used to transport oygen glucose and urea) Surace Tension The force of attraction #et%een %ater molecules maes %ater sufficiently dense for some smaller organisms to move along its surface 3.2.1 Distinguish et$een organic and inorganic compounds 8rganic compounds are compounds containing car#on that are found in living things - ecept hydrogen car#onates (,C8 3-) car#onates (C8 32-) and oides of car#on (C8 C8 2) ?norganic compounds are all other compounds (there are less different inorganic compounds than organic compounds)
Car#ohydrates are organic compounds consisting of one or more simple sugars that as monomers follo% the general #asic formula of (C, 28) ote: ceptions to this #asic formula and the inclusion of other atoms (e.g. ) can occur 3.2.2 "dentify glucose and riose from diagrams sho$ing their structure -lucose *C324$03+ Ribose *C524605+
3.2.3 /ist three e'amples each of monosaccharides, disaccharides and polysaccharides
Monosaccharides:
+lants (ructose: &ound in honey and onions it is very s%eet and a good source of energy Sucrose: sed primarily as a transporta#le energy form (e.g. sugar #eets and sugar cane) Cellulose: sed #y plant cells as a strengthening component of the cell %all
3.2.# Outline the role of condensation and hydrolysis in the relationship et$een monosaccharides, disaccharides and polysaccharides Condensation (dehydration) reactions occur %hen molecules are covalently $oined together and %ater is formed as a #y-product ?n car#ohydrates the #ond that is formed is called a glycosidic linage The opposite of a condensation reaction is a hydrolysis reaction %hich re=uires a %ater molecule to #rea a covalent #ond #et%een t%o su#units !onosaccharides are single monomers that are $oined to form disaccharides %hile sugars containing multiple su#units (more than 16) are called polysaccharides
A Condensation *eaction #et%een T%o !onosaccharides
'ipids are a group of organic molecules that are insolu#le in %ater #ut solu#le in non-polar organic solvents Common lipids include triglycerides (fats and oils) phospholipids and steroids 3.2.2 "dentify fatty acids from diagrams sho$ing their structure
;aturated (no dou#le nsaturated (dou#le #onds)
3.2.# Outline the role of condensation and hydrolysis in the relationship et$een fatty acids, glycerol and triglycerides A condensation reaction occurs #et%een the three hydroyl groups of glycerol and the car#oyl groups of three fatty acids This reaction forms a triglyceride (and three molecules of %ater) The #ond #et%een the glycerol and the fatty acids is an ester linage hen one of the fatty acids is replaced #y a phosphate group and phospholipid is formed ,ydrolysis reactions %ill in the presence of %ater #rea these molecules do%n into their constituent su#units
&ormation of a Triglyceride
3.2.% State three functions of lipids tructure: +hospholipids are a main component of cell mem#ranes ormonal si)nallin): ;teroids are involved in hormonal signalling (e.g. estrogen progesterone testosterone) nsulation: &ats in animals can serve as heat insulators %hile sphingolipids in the myelin sheath (of neurons) can serve as electrical insulators rotection: Triglycerides may form a tissue layer around many ey internal organs and provide protection against physical in$ury tora)e o ener)y: Triglycerides can #e used as a long-term energy storage source
3.2.( Compare the use of carohydrates and lipids in energy storage Similarities: Comple car#ohydrates (e.g. polysaccharides) and lipids #oth contain a lot of chemical energy and can #e used for energy storage Comple car#ohydrates and lipids are #oth insolu#le in %ater - they are not easily transported Car#ohydrates and lipids #oth #urn cleaner than proteins (they do not yield nitrogenous %astes) %ierences: 'ipid molecules contain more energy per gram than car#ohydrates (a#out t%ice as much) Car#ohydrates are more readily digested than lipids and release their energy more rapidly !onosaccharides and disaccharides are %ater solu#le and easier to transport to and from storage sites than lipids
Animals tend to use car#ohydrates primarily for short-term energy storage %hile lipids are used more for long-term energy storage Car#ohydrates are stored as glycogen in animals %hile lipids are stored as fats (in plants car#ohydrates are stored as cellulose and lipids as oils) 'ipids have less effect on osmotic pressure %ithin a cell than comple car#ohydrates
+roteins are large organic compounds made of amino acids arranged in a linear chain The se=uence of amino acids in a protein is defined #y a gene and encoded in the genetic code 3.2.2 "dentify amino acids from diagrams sho$ing their structure
Types of Amino Acids 3.2.# Outline the role of condensation and hydrolysis in the relationship et$een amino acids and polypeptides
A condensation reaction occurs #et%een the amino group (, 2) of one amino acid and the car#oylic acid group (C88,) of another amino acid This reaction forms a dipeptide (plus a molecule of %ater) that is held together #y a peptide #ond !ultiple amino acids can #e $oined together to form a polypeptide chain ?n the presence of %ater polypeptides can #e #roen do%n into individual amino acids via hydrolysis reactions &ormation of a ipeptide
3.3.1 Outline D nucleotide structure in terms of a sugar deo'yriose-, ase and phosphate
3.3.2 State the names of the four ases in D The four #ases in A are: Adenine Thymine
Adenine and guanine are purines (dou#le ring #ases) Thymine and cytosine are pyrimidines (single ring #ases) 3.3.3 Outline ho$ the D nucleotides are lin!ed together y covalent onds into a single strand
ucleotides a lined into a single strand via a condensation reaction The phosphate group (attached to the 4"-C of the sugar) $oins %ith the hydroyl (8,) group attached to the 3"-C of the sugar This results in a phosphodiester #ond #et%een the t%o nucleotides and the formation of a %ater molecule ;uccessive condensation reactions #et%een nucleotides results in the formation of a long single strand 3.3.4 &'plain ho$ a D doule heli' is formed using complementary ase pairing and hydrogen onds
T%o polynucleotide chains of A are held together #y hydrogen #onds #et%een complementary #ase pairs
Adenine pairs %ith thymine (AT) via t%o hydrogen #onds
Adenine Cytosine
?n order for #ases to #e facing each other and thus a#le to pair the t%o strands must run in opposite directions (i.e. they are anti-parallel) As the polynucleotide chain lengthens the atoms that mae up the molecule %ill arrange themselves in an optimal energy configuration This position of least resistance results in the dou#le-stranded A t%isting to form a dou#le heli %ith approimately 16 - 14 #ases per t%ist 3.3.# Dra$ and lael a simple diagram of the molecular structure of D
3.4.1 &'plain D replication in terms of un$inding of the doule heli' and separation of the strands y helicase, follo$ed y the formation of the ne$ complementary strands y D polymerase 2elicase n%inds the A and separates the t%o polynucleotide strands #y #reaing the hydrogen #onds #et%een complementary #ase pairs The t%o separated polynucleotide strands act as templates for the synthesis of ne% polynucleotide strands %N, !olymerase ;ynthesises ne% strands from the t%o parental template strands &ree deoynucleoside triphosphates (nucleotides %ith three phosphate groups) are aligned opposite their complementary #ase partner and are covalently #onded together #y A polymerase to form a complementary nucleotide chain The energy for this reaction comes from the cleavage of the t%o etra phosphate groups 3.4.2 &'plain the significance of complementary ase pairing in the conservation of the ase seuence of D ach of the nitrogenous #ases can only pair %ith its complementary partner (AT @ <C)
Conse=uently %hen A is replicated #y the com#ined action of helicase and A polymerase: The ne% strands formed %ill #e identical to the original strands separated from the template The t%o A molecules formed %ill #e identical to the original molecule A *eplication is a ;emi-Conservative +rocess
3.4.3 State that D replication is semi5conservative A replication is a semi-conservative process #ecause %hen a ne% dou#lestranded A molecule is formed: 8ne strand %ill #e from the original molecule 8ne strand %ill #e ne%ly synthesised 3.#.1 Compare the structure of D and 6
3.#.2 Outline D transcription in terms of the formation of an 6 strand complementary to the D strand y 6 polymerase Transcription is the process #y %hich an *A se=uence is produced from a A template: *A polymerase separates the A strands and synthesises a complementary *A copy from one of the A strands
?t does this #y covalently #onding ri#onucleoside triphosphates that align opposite their eposed complementary partner (using the energy from the cleavage of the additional phosphate groups to $oin them together) 8nce the *A se=uence has #een synthesised *A polymerase %ill detach from the A molecule and the dou#le heli %ill reform The se=uence of A that is transcri#ed into *A is called a gene Transcription occurs in the nucleus (%here the A is) and once made the m*A moves to the cytoplasm (%here translation can occur) Three main types of *A are predominantly made: !essenger *A (m*A): A transcript copy of a gene used to encode a polypeptide Transfer *A (t*A): A clover leaf shaped se=uence that carries an amino acid *i#osomal *A (r*A): A primary component of ri#osomes 3.#.3 Descrie the genetic code in terms of codons comprised of triplets of ases The genetic code is the set of rules #y %hich information encoded in m*A se=uences is converted into proteins (amino acid se=uences) #y living cells Codons are a triplet of #ases %hich encodes a particular amino acid As there are four #ases there are G different codon com#inations ( G) The order of the codons determines the amino acid se=uence for a protein The coding region al%ays starts %ith a ;TA*T codon (A<) and terminates %ith a ;T8+ codon
The
The genetic code has the follo%ing features: ?t is universal - every living thing uses the same code (there are only a fe% rare and minor eceptions) ?t is de)enerate - there are only 26 amino acids #ut G codons so more than one codon may code for the same amino acid (this allo%s for silent mutations %here#y a change in the A se=uence does not affect the polypeptide se=uence) 3.#.4 &'plain the process of translation, leading to polypeptide formation Translation is the process of protein synthesis in %hich the genetic information encoded in m*A is translated into a se=uence of amino acids in a polypeptide chain *i#osomes #ind to m*A in the cell"s cytoplasm and move along the m*A molecule in a 4" - 3" direction until it reaches a start codon (A<) Anticodons on t*A molecules align opposite appropriate codons according to complementary #ase pairing (e.g. AC %ill align %ith A<) ach t*A molecule carries a specific amino acid (according to the genetic code) *i#osomes catalyse the formation of peptide #onds #et%een ad$acent amino acids (via a condensation reaction) The ri#osome moves along the m*A molecule synthesising a polypeptide chain until it reaches a stop codon at this point translation stops and the polypeptide chain is released
The +rocess of Translation
3.#.# &'plain the relationship et$een one gene and one polypeptide A gene is a se=uence of A %hich encodes a polypeptide se=uence A gene se=uence is converted into a polypeptide se=uence via the processes of transcription (maing an m*A transcript) and translation (polypeptide synthesis) Translation uses t*A molecules and ri#osomes to $oin amino acids into a polypeptide chain according to the m*A se=uence (as read in codons) The universality of the genetic code means all organisms sho% the same relationship #et%een genes and polypeptides (indicating a common ancestry and allo%ing for transgenic techni=ues to #e employed) ;ome proteins may consist of a num#er of polypeptide chains and thus need multiple genes (e.g. haemoglo#in consists of four polypeptide su#units encoded #y t%o different genes) hen a gene is mutated it may lead to the synthesis of a defective polypeptide hence affecting protein function
The "8ne
There are t%o eceptions to the "one gene - one polypeptide" rule:
Active site and su#strate complement each other in terms of #oth shape and chemical properties (e.g. opposite charges) 7inding to the active site #rings the su#strate into close physical proimity creating an en0yme-su#strate comple The en0yme catalyses the conversion of the su#strate into a product (or products) creating an en0yme-product comple As the en0yme is not consumed in the reaction it can continue to %or once the product dissociates (hence only lo% concentrations are needed) n0yme-;u#strate ;pecificity
.oc" and 7ey Model n0ymes and su#strates share specificity (a given en0yme %ill only interact %ith a small num#er of specific su#strates that complement the active site) This eplanation of en0yme-su#strate interaction is descri#ed as the "loc and ey" model (a loc only opens in response to a specific ey)
Compare %ith ?nduced &it !odel (/.G.2)
3.%.3 &'plain the effects of temperature, p7 and sustrate concentration on enzyme activity Temperature 'o% temperatures result in insufficient thermal energy for the activation of a given en0yme-catalysed reaction to #e achieved ?ncreasing the temperature %ill increase the speed and motion of #oth en0yme and su#strate resulting in higher en0yme activity This is #ecause a higher inetic energy %ill result in more fre=uent collisions #et%een en0yme and su#strate At an optimal temperature (may differ for different en0ymes) the rate of en0yme activity %ill #e at its pea ,igher temperatures %ill cause en0yme sta#ility to decrease as the thermal energy disrupts the hydrogen #onds holding the en0yme together This causes the en0yme (particularly the active site) to lose its shape resulting in a loss of en0yme activity (denaturation) p2
Changing the p, %ill alter the charge of the en0yme %hich in turn %ill protein solu#ility and may change the shape of the molecule Changing the shape or charge of the active site %ill diminish its a#ility to #ind to the su#strate a#rogating en0yme function n0ymes have an optimum p, (may differ #et%een en0ymes) and moving outside of this range %ill al%ays result in a diminished rate of reaction Substrate Concentration ?ncreasing su#strate concentration %ill increase the activity of a particular en0yme !ore su#strate means there is an increased lielihood of en0yme and su#strate colliding and reacting such that more reactions %ill occur and more products %ill #e formed in a given time period After a certain point the rate of reaction %ill cease to rise regardless of further increases to su#strate concentration as the environment has #ecome saturated %ith su#strate and all en0ymes are #ound and reacting (5 ma)
&actors Affecting n0yme Activity
3.%.4 Define denaturation enaturation is a structural change in a protein that results in the loss (usually permanent) of its #iological properties ,eat and p, are t%o agents %hich may cause denaturation of an en0yme
enaturation
3.%.# &'plain the use of lactase in the production of lactose5free mil!
'actose is a disaccharide of glucose and galactose %hich can #e #roen do%n #y the en0yme lactase ,istorically mammals ehi#it a mared decrease in lactase production after %eaning - leading to lactose intolerance (incidence is particularly high in Asian African ative American A#original populations)
'actose-free mil can #e produced #y purifying lactase (e.g. from yeast or #acteria) and #inding it to an inert su#stance (such as alginate #eads) !il passed over this immo#ilised en0yme %ill #ecome lactose-free
The generation of lactose-free mil can #e used in a num#er of %ays: As a source of mil for lactose-intolerant individuals As a means to increase the s%eetness of mil (glucose and galactose are s%eeter in flavour) thus negating the need for artificial s%eeteners As a %ay of reducing the crystallisation of ice-creams (glucose and galactose are more solu#le than lactose) As a means of shortening the production time for yogurts or cheese (#acteria ferment glucose and galactose more readily than lactose) 3.(.1 Define cell respiration Cell respiration is the controlled release of energy from organic compounds in cells to form AT+ (adenosine triphosphate)
3.(.2 State that, in cell respiration, glucose in the cytoplasm is ro!en do$n y glycolysis into pyruvate, $ith a small yield of 0
Anaero#ic *espiration
The conversion of pyruvate occurs in the cytoplasm of the cell and the products are: 'actate (3C) in animal cells thanol (2C) and car#on dioide (C8 2) in plants fungi (e.g. yeast) and #acteria The conversion of pyruvate into ethanol and C8 2 is also no%n as fermentation 3.(.4 &'plain that, during aeroic cell respiration, pyuvate can e ro!en do$n in the mitochondrion into caron dio'ide and $ater $ith a large yield of 0 Aero#ic respiration occurs in the presence of oygen and taes place in the mitochondrion +yruvate is #roen do%n into car#on dioide and %ater and a large amount of AT+ is formed (3 - 3G molecules) Although this process #egins %ith glycolysis (to #rea do%n glucose into pyruvate) glycolysis does not re=uire oygen and is an anaero#ic process
Anaero#ic versus Aero#ic *espiration
3.).1 State that photosynthesis involves the conversion of light energy into chemical energy +hotosynthesis is the process #y %hich plants synthesise organic compounds (e.g. glucose) from inorganic compounds (C8 2 and ,28) in the presence of sunlight
+hotosynthesis is a t%o step process: 1. The light dependent reactions convert the light energy into chemical energy (AT+) 2. The light independent reactions use the chemical energy to synthesise organic compounds (e.g. glucose) The organic molecules produced in photosynthesis can #e used in cellular respiration to provide the energy needed #y the organism 3.).2 State that light from the Sun is composed of a range of $avelengths colours-
;unlight is %hite light made up of all the colours of the visi#le spectrum Colours are different %avelengths of light and range from J 66 nm - /66 nm The colours of the visi#le spectrum are (from longer to shorter %avelength): ed
ran)e
ellow
reen
lue
ndi)o
iolet (*.8.K.<.7.?.5)
3.).3 State that chlorophyll is the main photosynthetic pigment Chlorophyll is the main site of light a#sorption in the light dependent stage of photosynthesis There are a num#er of different chlorophyll molecules each %ith their o%n distinct a#sorption spectra (the spectrum of light a#sor#ed #y a su#stance) hen chlorophyll a#sor#s light energy they release electrons %hich are used to mae AT+ (chemical energy)
Chlorophyll and +hotosystems
3.).4 Outline the difference in asorption of red, green and lue light y chlorophyll The main colours of light a#sor#ed #y chlorophyll are red and blue light The main colour of light not a#sor#ed (it is reflected) #y chlorophyll is )reen light This eplains %hy leaves are green - ecepting %hen the presence of other pigmented su#stances (e.g. anthocyanins) produces a different colour eciduous trees stop producing high amounts of chlorophyll in the %inter (due to insufficient sunlight) allo%ing other photosynthetic pigments (e.g. anthophylls carotenoids) to come to the fore %hich changes the colour of the leaf 3.).# State that light energy is used to produce 0, and to split $ater molecules photolysis- to form o'ygen and hydrogen
The first part of photosynthesis is the light dependent reaction %hich uses light energy to mae AT+
.i)ht %ependent Reaction 'ight stimulates chlorophyll to release electrons %hich results in the production of AT+ 'ight energy also splits %ater molecules (photolysis) producing oygen and hydrogen The hydrogen is taen up #y a hydrogen carrier (A+ H) to form A+, The splitting of %ater also releases electrons %hich replace those lost #y the chlorophyll The AT+ and hydrogen (A+,) are taen to the site of the light independent reactions 3.).% State that 0 and hydrogen derived from the photolysis of $ater- are used to fi' caron molecules to ma!e organic molecules The second part of photosynthesis is the light independent reaction %hich maes organic compounds from the products of the light dependent reactions
.i)ht 1ndependent Reaction AT+ and hydrogen (carried #y A+,) are products of the light dependent reactions They are used to fi car#on molecules together (add C8 2to #asic car#on compounds) This allo%s for the production of more comple organic molecules (e.g. sugars) These organic molecules can then #e stored to use in cellular respiration as re=uired 3.).( &'plain that the rate of photosynthesis can e measured directly y the production of o'ygen or the upta!e of caron dio'ide, or indirectly y an increase in iomass The rate of photosynthesis can #e measured #y changes in the amounts of inputs (C8 2) or outputs (8 2 or glucose) of the photosynthesis e=uation ater cannot #e measured as it is involved in a num#er of essential processes #esides photosynthesis (e.g. condensation and hydrolysis reactions) Measurin) C0$ Upta"e C82 uptae can #e measured #y placing a plant in an enclosed space %ith %ater Car#on dioide interacts %ith the %ater molecules producing #icar#onate and hydrogen ions %hich increases the acidity of the resulting solution The change in p, can therefore provide a measure of C8 2 uptae #y a plant (increased C8 2 uptae more alaline p,) Measurin) 0$ !roduction 82 production can #e measured #y su#merging a plant in an enclosed space %ith %ater attached to a sealed gas syringe Any oygen gas produced %ill #u##le out of solution and can #e measured #y a change in %ater level (via the position of the meniscus) Measurin) #iomass *1ndirect+
3.).) Outline the effect of temperature, light intensity and caron dio'ide concentration on the rate of photosynthesis Temperature +hotosynthesis is controlled #y en0ymes %hich are sensitive to temperature As temperature increases the rate of photosynthesis %ill increase as reagents have greater inetic energy and are more liely to react A#ove a certain temperature the rate of photosynthesis %ill decrease as essential en0ymes #egin to denature .i)ht 1ntensity As light intensity increases the rate of photosynthesis %ill increase up until a certain point %hen photosynthesis is proceeding at its maimum rate &urther increases to light intensity %ill have no effect on photosynthesis (the rate %ill plateau) as chlorophyll are saturated #y light ifferent %avelengths of light %ill have different effects on the rate of photosynthesis (e.g. green light %ill not #e used) C0$ Concentration As the concentration of car#on dioide increases the rate of photosynthesis %ill increase up until a certain point %hen photosynthesis is proceeding at its maimum rate &urther increases to car#on dioide concentration %ill have no effect on photosynthesis (the rate %ill plateau) as the en0ymes responsi#le for car#on fiation #ecome saturated
&actors Affecting the *ate of +hotosynthesis
4.1.1 State that eu!aryotic chromosomes are made of D and protein uaryotic chromosomes consist of A %rapped around histone proteins This forms the #asic structure of the nucleosome %hich is paced together to form chromatin (in a "#eads on a string" arrangement)
Chromatin %ill supercoil and condense during prophase to form chromosomes that can #e visualised under a light microscope +roaryotic A is not %rapped around proteins and is thus considered to #e "naed" Arrangement of A into chromosomes
4.1.2 Define gene, allele and genome -ene: A herita#le factor that controls a specific characteristic consisting of a length of A occupying a particular position on a chromosome (locus) ,llele: 8ne specific form of a gene differing from other alleles #y one or a fe% #ases only and occupying the same locus as other alleles of the gene -enome: The %hole of the genetic information of an organism 4.1.3 Define gene mutation -ene mutation: A change in the nucleotide se=uence of a section of A coding for a particular feature
Types of !utations 4.1.4 &'plain the conseuence of a ase sustitution mutation in relation to the process of transcription and translation using the e'ample of sic!le cell anaemia Cause o Sic"le Cell ,naemia A #ase su#stitution mutation is the change of a single #ase in a se=uence of A resulting in a change to a single m*A codon during transcription ?n the case of sicle cell anaemia the Gth codon for the #eta chain of haemoglo#in is changed from
ormal *ed 7lood Cell ;icle Cell
Conse8uences o Sic"le Cell ,naemia The insolu#le haemoglo#in cannot effectively carry oygen causing individual to feel constantly tired The sicle cells may accumulate in the capillaries and form clots #locing #lood supply to vital organs and causing a myriad of health pro#lems Also causes anaemia (lo% *7C count) as the sicle cells are destroyed more rapidly than normal red #lood cells ;icle cell anaemia occurs in individuals %ho have t%o copies of the codominant "sicle cell" allele (i.e. homo0ygotes) ,etero0ygous individuals have increased resistance to malaria due to the presence of a single "sicle cell" allele (hetero0ygous advantage)
;icle Cell Anaemia
4.2.1 State that meiosis is a reduction division of a diploid nucleus to form haploid nuclei
!eiosis is the process #y %hich se cells (gametes) are made in the reproductive organs: !ost seually reproducing animals are diploid - meaning they have t%o copies of every chromosome (one of maternal origin one of paternal origin) ?n order to reproduce these organisms need to mae gametes that are haploid (have only one copy of each chromosome) &ertilisation of t%o haploid gametes (egg H sperm) %ill result in the formation of a diploid 0ygote that %ill gro% into a ne% organism !eiosis consists of t%o cell divisions: The first division is a reduction division of the diploid nucleus to form haploid nuclei The second division separates sister chromatids (this division is necessary #ecause meiosis is preceded #y interphase %herein A is replicated) 4.2.2 Define homologous chromosomes ,omologous chromosomes are chromosomes that share: The same structural features (e.g. same si0e same #anding pattern same centromere position) The same genes at the same loci positions (%hile genes are the same alleles may #e different) 4.2.3 Outline the process of meiosis, including pairing of homologous chromosomes and crossing over, follo$ed y t$o divisions, $hich results in four haploid cells The process of meiosis involves t%o divisions #oth of %hich follo% the same #asic stages as mitosis (prophase metaphase anaphase and telophase) !eiosis is preceded #y interphase %hich includes the replication of A (; phase) to create chromosomes %ith genetically identical sister chromatids
Meiosis 1 ,omologous chromosomes must first pair up in order to #e sorted into separate haploid daughter cells ?n prophase ? homologous chromosomes undergo a process called synapsis %here#y homologous chromosomes pair up to form a #ivalent (or tetrad)
The homologous chromosomes are held together at points called chiasma (singular: chiasmata) Crossing over of genetic material #et%een non-sister chromatids can occur at these points resulting in ne% gene com#inations (recom#ination) The remainder of meiosis ? involves separating the homologous chromosomes into separate daughter cells ?n metaphase ? the homologous pairs line up along the e=uator of the cell ?n anaphase ? the homologous chromosomes split apart and move to opposite poles ?n telophase ? the cell splits into t%o haploid daughter cells as cytoinesis happens concurrently Meiosis 11 ?n meiosis ?? the sister chromatids are divided into separate cells ?n prophase ?? spindle fi#res reform and reconnect to the chromosomes ?n metaphase ?? the chromosomes line up along the e=uator of the cell ?n anaphase ?? the sister chromatids split apart and move to opposite poles ?n telophase ?? the cell splits in t%o as cytoinesis happens concurrently
7ecause sister chromatids may no longer #e genetically identical as a result of potential recom#ination the process of meiosis results in the formation of four genetically distinct haploid daughter cells
4.2.4 &'plain that non5dis8unction can lead to a change in chromosome numer, illustrated y reference to Do$n syndrome trisomy 21on-dis$unction refers to the chromosomes failing to separate correctly resulting in gametes %ith one etra or one missing chromosome (aneuploidy) The failure of the chromosomes to separate may either occur via: &ailure of homologues to separate during Anaphase ? (resulting in four affected daughter cells) &ailure of sister chromatids to separate during Anaphase ?? (resulting in t%o affected daughter cells)
on-is$unction
?ndividuals %ith o%n syndrome have three copies of chromosome 21 (trisomy 21) 8ne of the parental gametes had t%o copies of chromosome 21 as a result of non-dis$unction The other parental gamete %as normal and had a single copy of chromosome 21 hen the t%o gametes fused during fertilisation the resulting 0ygote had three copies of chromosome 21 leading to o%n syndrome 4.2.# State that, in !aryotyping, chromosomes are arranged in pairs according to their structure A aryotype is a visual profile of all the chromosomes in a cell The chromosomes are arranged into homologous pairs and displayed according to their structural characteristics
,uman !ale Laryotype
Laryotyping involves: ,arvesting cells (usually from foetus or %hite #lood cells of adults) Chemically inducing cell division then halting it during mitosis %hen chromosomes are condensed and thus visi#le The stage during %hich mitosis is halted %ill determine %hether chromosomes appear %ith sister chromatids ;taining and photographing chromosomes #efore arranging them according to structure 4.2.% State that !aryotyping is performed using cells collected y chorionic villus sampling or amniocentesis, for pre5natal diagnosis of chromosome anormalities +re-natal aryotyping is often used to: etermine the gender of an un#orn child (via identification of se chromosomes) Test for chromosomal a#normalities (e.g. aneuploidies resulting from nondis$unction) ,mniocentesis A needle is inserted through the a#dominal %all into the amniotic cavity in the uterus and a sample of amniotic fluid containing foetal cells is taen ?t can #e done at J 1Gth %ee of pregnancy %ith a slight chance of miscarriage (J6.4F) Chorionic 9illus Samplin) A tu#e is inserted through the cervi and a tiny sample of the chorionic villi (contains foetal cells) from the placenta is taen
?t can #e done at J 11th %ee of pregnancy %ith a slight ris of inducing miscarriage (J1F)
Amniocentesis Chorionic 5illus ;ampling
4.2.( nalyse a human !aryotype to determine gender and $hether non5 dis8unction has occurred very cell in the human #ody has G chromosomes (ecept anucleate red #lood cells and haploid gametes) !ales (MK) and females (MM) can #e differentiated on the #asis of their se chromosomes on-dis$unction during gamete formation can lead to individuals %ith an a#normal num#er of chromosomes (aneuploidy) These disorders can #e classified according to the chromosome num#er affected and the num#er of chromosomes present 4.3.1 Define genotype, phenotype, dominant allele, recessive allele, codominant alleles, locus, homozygous, heterozygous, carrier and test cross -enotype: The allele com#ination of an organism !henotype: The characteristics of an organism (determined #y a com#ination of genotype and environmental factors) %ominant ,llele: An allele that has the same effect on the phenotype %hether it is present in the homo0ygous or hetero0ygous state Recessive ,llele: An allele that only has an effect on the phenotype %hen present in the homo0ygous state Codominant ,lleles: +airs of alleles that #oth affect the phenotype %hen present in a hetero0ygote .ocus: The particular position on homologous chromosomes of a gene 2omozy)ous: ,aving t%o identical alleles of a gene 2eterozy)ous: ,aving t%o different alleles of a gene
Carrier: An individual that has one copy of a recessive allele that causes a genetic disease in individuals that are homo0ygous for this allele Test Cross: Testing a suspected hetero0ygote #y crossing it %ith a no%n homo0ygous recessive 4.3.2 Determine the genotypes and phenotypes of the offspring of a monohyrid cross using a unnett grid A genetic cross is a means of determining the genetic characteristics of potential offspring #ased on the genetic characteristics of the prospective parents A monohy#rid cross determines the allele com#inations of offspring for one particular gene only (,' students may refer to topic 16.2 for dihy#rid crosses)
!onohy#rid crosses can #e calculated according to the follo%ing steps: Step 4: esignate characters to represent the alleles Capital letter for dominant allele lo%er case letter for recessive allele Step $: rite do%n the genotype and phenotype of the parents This is the + generation (parental generation) Step &: rite do%n the genotype of the parental gametes These %ill #e haploid as a result of meiotic division Step : se a +unnett grid to %or out the potential gamete com#inations
As fertilisation is random all com#inations have an e=ual pro#a#ility Step 5: rite out the genotype and phenotype ratios of potential offspring This is the & 1 generation (first filial generation) ;u#se=uent generations through inter#reeding la#eled & 2 &3 etc. Note: The genotypic and phenotypic ratios calculated are only pro#a#ilities
4.3.3 State that some genes have more than t$o alleles multiple alleles;ome genes have more than t%o alleles for a given trait (e.g. the A78 #lood group system) The alleles %hich are not recessive may either: ;hare codominance (#e epressed e=ually in the phenotype) ;hare incomplete dominance (neither is fully epressed in the phenotype resulting in #lending) emonstrate a dominance order (e.g. allele A N allele 7 N allele C) 4.3.4 Descrie 9O lood groups as an e'ample of codominance and multiple alleles hen assigning alleles for codominance the convention is to use a common letter to represent dominant and recessive and use superscripts to represent the different codominant alleles ? stands for immunoglo#ulin (antigenic protein on #lood cells) A and 7 stand for the codominant variants
The A78 gene has three alleles: ? A ?7 and i ? A and ? 7 are codominant %herease i is recessive (no antigenic protein is produced) Codominance means that #oth ? A and ? 7 alleles %ill #e epressed %ithin a given phenotype The genotypes and phenotypes of the A78 #lood groups are:
The A78 7lood
4.3.# &'plain ho$ se' chromosomes control gender y referring to the inheritance of : and ; chromosomes in humans ,umans have 23 pairs of chromosomes for a total of G (ecluding instances of aneuploidy) The first 22 pairs are autosomes - each chromosome pair possesses the same genes and structural features The 23rd pair of chromosomes are heterosomes (or se chromosomes) and determine gender &emales are MM - they possess t%o M chromosomes !ales are MK - they posses one M chromosome and a much shorter K chromosome
The K chromosome contains the genes for developing male se characteristic hence the father is al%ays responsi#le for determining gender ?f the male sperm contains the M chromosome the gro%ing em#ryo %ill develop into a girl ?f the male sperm contains a K chromosome the gro%ing em#ryo %ill develop into a #oy ?n all cases the female egg %ill contain an M chromosome (as the mother is MM)
7ecause the M and K chromosomes are of a different si0e they cannot undergo crossing over recom#ination during meiosis This ensures that the gene responsi#le for gender al%ays remains on the K chromosome meaning that there is al%ays J 46F chance of a #oy or girl 4.3.% State that some genes are present on the : chromosome and asent from the shorter ; chromosome
The K chromosome is much shorter than the M chromosome and contains only a fe% genes ?ncludes the ;*K se-determination gene and a fe% others (e.g. hairy ears gene) The M chromosome is much longer and contains several genes not present on the K chromosome ?ncludes the genes for haemophilia and red-green colour #lindness ?n human females only one of the M chromosomes remains active throughout life The other is pacaged as heterochromatin to form a condensed 7arr #ody This inactivation is random and individual to each cell so hetero0ygous %omen %ill #e a mosaic - epressing #oth alleles via different cells 4.3.( Define se' lin!age
;e linage refers to %hen a gene controlling a characteristic is found on a se chromosome (and so %e associate the trait %ith a predominant gender) ;e-lined conditions are usually M-lined as very fe% genes eist on the shorter K chromosome 4.3.) Descrie the inheritance of colour lindness and haemophilia as e'amples of se' lin!age Colour #lindness and haemophilia are #oth eamples of M-lined recessive conditions The gene loci for these conditions are found on the non-homologous region of the M chromosome (they are not present of the K chromosome) As males only have one allele for this gene they cannot #e a carrier for the condition This means they have a higher fre=uency of #eing recessive and epressing the trait !ales %ill al%ays inherit an M-lined recessive condition from their mother &emales %ill only inherit an M-lined recessive condition if they receive a recessive allele from #oth parents
hen assigning alleles for se-lined traits the convention is to %rite the allele as a superscript to the se chomosome (usually M) 2aemophilia: M, unaffected @ M h affected Colour #lindness: M A unaffected @ M a affected !ale and &emale
4.3.* State that a human female can e homozygous or heterozygous $ith respect to se'5lin!ed genes As human females have t%o M chromosomes (and therefore t%o alleles for any given M-lined gene) they can #e either homo0ygous or hetero0ygous !ales only have one M chromosome (and therefore only one allele) and are hemi0ygous 4.3.1+ &'plain that female carriers are heterozygous for :5lin!ed recessive alleles
An individual %ith a recessive allele for a disease condition that is mased #y a normal dominant allele is said to #e a carrier Carriers are hetero0ygous and can potentially pass the trait on to the net generation #ut do not suffer from the defective condition themselves &emales can #e carriers for M-lined recessive conditions #ecause they have t%o M chromosomes - males (MK) cannot #e carriers 7ecause a male only inherits an M chromosome from his mother his chances of inheriting the disease condition from a carrier mother is greater 4.3.11 redict the genotypic and phenotypic ratios of offspring of monohyrid crosses involving any of the aove patterns of inheritance ,utosomal %ominance ; Recessive Choose a letter %here the upper and lo%er case forms are easily distinguisha#le (e.g. e Aa 7#) se the capital letter for the dominant allele and the lo%er case letter for the recessive allele ample:
Codominance Choose a letter to denote the general trait encoded #y the gene (capital dominant lo%er case recessive) se different superscript letters (capitals) to represent the different codominant alleles ample:
<=lin"ed Recessive se a capital OMO to denote the M chromosome Choose a superscript letter to represent the trait (capital dominant lo%er case recessive) ample:
4.3.12 Deduce the genotype and phenotype of individuals in pedigree charts A pedigree is a chart of the genetic history of a family over several generations !ales are represented as s=uares %hile females are represented as circles ;haded sym#ols means an individual is affected #y a condition %hile an unshaded sym#ol means they are unaffected A hori0ontal line #et%een a man and %oman represents mating and resulting children are sho%n as offshoots to this line ,utosomal %ominance All affected individuals must have at least one affected parent ?f t%o parents are unaffected all offspring must #e unaffected (homo0ygous recessive) ?f t%o parents are affected they may have offspring %ho are unaffected (if parents are hetero0ygous) ,utosomal Recessive ?f t%o parents sho% a trait all children must also sho% the trait (homo0ygous recessive) An affected individual may have t%o normal parents (if parents are #oth hetero0ygous carriers) <=.in"ed Recessive ?f a female sho%s the trait so must all sons as %ell as her father The disorder is more common in males
?dentifying !odes of ?nheritance
4.4.1 Outline the use of polymerase chain reaction C6- to copy and amplify minute uantities of D <
+C* is a %ay of producing large =uantites of a specific target se=uence of A ?t is useful %hen only a small amount of A is avalia#le for testing .g. crime scene samples of #lood semen tissue hair etc. +C* occurs in a thermal cycler and involves a repeat procedure of 3 steps: 1. %enaturation: A sample is heated to separate it into t%o strands 2. ,nnealin): A primers attach to opposite ends of the target se=uence 3. Elon)ation: A heat-tolerant A polymerase (Ta=) copies the strands
8ne cycle of +C* yields t%o identical copies of the A se=uence A standard reaction of 36 cycles %ould yield 16/3/1B2G copies of A 36 (2 ) 4.4.2 State that, in gel electrophoresis, fragments of D can move in an electric field and are separated according to their size
;amples of fragmented A are placed in the %ells of an agarose gel The gel is placed in a #uffering solution and an electrical current is passed across the gel A #eing negatively charged (due to phosphate) moves to the positive terminus (anode) ;maller fragments are less impeded #y the gel matri and move faster through the gel The fragments are thus separated according to si0e ;i0e can #e calculated (in ilo#ases) #y comparing against a no%n industry standard 4.4.3 State that gel electrophoresis of D is used in D profiling A profiling is a techni=ue #y %hich individuals are identified on the #asis of their respective A profiles ithin the non-coding region of an individual"s genome there eists satellite A - long stretches of A made up of repeating elements called short tandem repeats (;T*s) These repeating se=uences can #e ecised to form fragments #y cutting %ith a variety of restriction endonucleases (%hich cut A at specific sites) As individuals all have a different num#er of repeats in a given se=uence of satellite A they %ill all generate uni=ue fragment profiles These different profiles can #e compared using gel electrophoresis
A +rofiling sing ;T* Analysis
4.4.4 Descrie the application of D profiling to determine paternity and also in forensic investigation A A sample is collected (#lood saliva semen etc.) and amplified using +C* ;atellite A (non-coding) is cut %ith specific restriction en0ymes to generate fragments ?ndividuals %ill have uni=ue fragment lengths due to the varia#le length of their short tandem repeats (;T*) The fragments are separated %ith gel electrophoresis (smaller fragments move =uicer through the gel) The A profile can then #e analysed according to need
T%o applications of A profiling are: +aternity testing (comparing A of offspring against potential fathers) &orensic investigations (identifying suspects or victims #ased on crimescene A) 4.4.# nalyse D profiles to dra$ conclusions aout paternity or forensic investigations +aternity Testing: Children inherit half of their alleles from each parent and thus should possess a com#ination of their parents alleles &orensic ?nvestigation: ;uspect A should #e a complete match %ith the sample taen from a crime scene if a conviction is to occur
+aternity Test &orensic ?nvestigation
4.4.% Outline three outcomes of the seuencing of the complete human genome The ,uman
ith the completion of the ,uman
The genetic code is universal meaning that for every living organism the same codons code for the same amino acids (there are a fe% rare eceptions) This means that the genetic information from one organism could #e translated #y another (i.e. it is theoretically transfera#le) Current amples of Transgenic !odification
4.4.) Outline a asic techniue used for gene transfer involving plasmids, a host cell acterium, yeast or other cell-, restriction enzymes endonucleases- and D ligase 4> %N, Extraction A plasmid is removed from a #acterial cell (plasmids are small circular A molecules that can eist and replicate autonomously) A gene of interest is removed from an organism"s genome using a restriction endonuclease %hich cut at specific se=uences of A The gene of interest and plasmid are #oth amplified using +C* technology $> %i)estion and .i)ation The plasmid is cut %ith the same restriction en0yme that %as used to ecise the gene of interest Cutting %ith certain restriction en0ymes may generate short se=uence overhangs (Osticy endsO) that allo% the the t%o A constructs to fit together The gene of interest and plasmid are spliced together #y A ligase creating a recom#inant plasmid &> Transection and Expression The recom#inant plasmid is inserted into the desired host cells (this is called transfection for euaryotic cells and transformation for proaryotic cells) The transgenic cells %ill hopefully produce the desired trait encoded #y the gene of interest (epression) The product may need to su#se=uently #e isolated from the host and purified in order to generate sufficient yield
Treating ,aemophilia via the ?solation of ,uman &actor ?M Clotting +rotein from Transgenic ;heep !il
4.4.* State t$o e'amples of current uses of genetically modified crops or animals Crops 1. &ngineering crops to e'tend shelf life of fresh produce Tomatoes (&lavr ;avr) have #een engineered to have an etended eeping =uality #y s%itching off the gene for ripening and thus delaying the natural process of softening of fruit 2. &ngineering of crops to provide protection from insects !ai0e crops (7t corn) have #een engineered to #e toic to the corn #orer #y introducing a toin gene from a #acterium ( 9acillus thuringiensis ) ,nimals 1. &ngineering animals to enhance production ;heep produce more %ool %hen engineered %ith the gene for the en0yme responsi#le for the production of cysteine - the main amino acid in the eratin protein of %ool 2. &ngineering animals to produce desired products ;heep engineered to produce human alpha-1-antitrypsin in their mil can #e used to help treat individuals suffering from hereditary emphysema 4.4.1+ Discuss the potential enefits and potential harmful effects of one e'ample of genetic modification
Example: !ai0e introduced %ith a #acterial gene encoding a toin to the uropean Corn 7orer (i.e. 7t Corn)
+otential 7enefits Allo%s for the introduction of a characteristic that %asn"t present %ithin the gene pool (selective #reeding could not have produced desired phenotype) *esults in increased productivity of food production (re=uires less land for compara#le yield) 'ess use of chemical pesticides reducing the economic cost of farming Can no% gro% in regions that previously may not have #een via#le (reduces need for deforestation) +otential ,armful ffects Could have currently unno%n harmful effects (e.g. toin may cause allergic reactions in a percentage of the population) Accidental release of transgenic organism into the environment may result in competition %ith native plant species +ossi#ility of cross pollination (if gene crosses the species #arrier and is introduced to %eeds may have a hard time controlling %eed gro%th) *educes genetic variation #iodiversity (corn #orer may play a crucial role in local ecosystem) 4.4.11 Define clone A clone is a group of genetically identical organisms or a group of cells derived from a single parent cell
4.4.12 Outline a techniue for cloning using differentiated animal cells ;omatic Cell uclear Transfer (;CT) is a method of reproductive cloning using differentiated animal cells A female animal (e.g. sheep) is treated %ith hormones (such as &;,) to stimulate the development of eggs The nucleus from an egg cell is removed (enucleated) there#y removing the genetic information from the cell The egg cell is fused %ith the nucleus from a somatic (#ody) cell of another sheep maing the egg cell diploid An electric shoc is delivered to stimulate the egg to divide and once this process has #egun the egg is implanted into the uterus of a surrogate The developing em#ryo %ill have the same genetic material as the sheep that contri#uted the diploid nucleus and thus #e a clone
ifferent ses of Cloning
4.4.13 Discuss the ethical issues of therapeutic cloning in humans *efer to Topic 2.1.16 for an outline of uses for therapeutic cloning in humans ,r)uments or Therapeutic Clonin) !ay #e used to cure serious diseases or disa#ilities %ith cell therapy (replacing #ad cells %ith good ones) ;tem cell research may pave the %ay for future discoveries and #eneficial technologies that %ould not have occurred if their use had #een #anned ;tem cells can #e taen from em#ryos that have stopped developing and %ould have died any%ay (e.g. a#ortions) Cells are taen at a stage %hen the em#ryo has no nervous system and can argua#ly feel no pain ,r)uments ,)ainst Therapeutic Clonin) ?nvolves the creation and destruction of human em#ryos (at %hat point do %e afford the right to lifeP) m#ryonic stem cells are capa#le of continued division and may develop into cancerous cells and cause tumors !ore em#ryos are generally produced than are needed so ecess em#ryos are illed ith additional cost and effort alternative technologies may fulfil similar roles (e.g. nuclear reprogramming of differentiated cell lines) %.1.1 &'plain $hy digestion of large food molecules is essential !ost food is solid and in the form of large comple molecules %hich are insolu#le and chemically inert (not readily usa#le) As food %as synthesised #y other organisms it contains materials not suita#le for human tissue - these need to #e separated and removed
'arge molecules need to #e #roen do%n into smaller molecules that can #e readily a#sor#ed across mem#ranes and into cells ;mall molecules can #e reassem#led into ne% products (e.g. amino acids can #e reassem#led to mae ne% proteins)
%.1.2 &'plain the need for enzymes in digestion n0ymes are #iological catalysts %hich speed up the rate of a chemical reaction (e.g. digestion) #y lo%ering the activation energy n0ymes allo% digestive processes to occur at #ody temperature and at sufficient speed to meet the organism"s survival re=uirements n0ymes are specific for a given su#strate and so can allo% digestion of certain molecules to occur independently of others %.1.3 State the source, sustrate, product and optimal p7 conditions for one amylase, one protease and one lipase
%.1.4 Dra$ and lael a diagram of the human digestive system There are t%o ma$or groups of organs that comprise the human digestive system: ,limentary Canal: Contains organs through %hich the food actually passes (esophagus stomach small intestine large intestine etc.) ,ccessory 0r)ans: 8rgans that assist in digestion #ut no food passes through them (liver pancreas gall #ladder salivary glands etc.)
Alimentary Canal Accessory 8rgans
%.1.# Outline the function of the stomach, small intestine and large intestine Stomach The stomach acts as a temporary storage tan and is %here protein digestion #egins The stomach contains gastric glands %hich secrete digestive $uices for chemical digestion Acids create a lo% p, environment (p,J1-2) that denatures proteins %hile proteases lie pepsin hydrolyse large proteins
The stomach also releases a hormone (gastrin) that regulates stomach secretions The mechanical action of the stomach (churning) also promotes digestion #y miing the food The stomach turns food into a creamy paste called chyme Small 1ntestine The small intestine is %here usua#le food su#stances (e.g. nutrients) are a#sor#ed into the #loodstream The pancreas and gall #ladder (via the #ile duct) #oth secrete su#stances into the small intestine to aid in digestion The small intestine is lined %ith smooth muscle to allo% for the miing and moving of digested food products (via segmentation and peristalsis) ?t also contains small pits (crypts of lie#eruhn) that secrete intestinal $uices The small intestine contain infoldings called villi to increase surface area and optimise the rate of a#sorption .ar)e 1ntestine The large intestine a#sor#s %ater and dissolved minerals from the indigesti#le food residues and #y doing so converts %hat remains from a fluid state into a semi-solid faeces The faeces is stored in the rectum and eliminated out the anus %.1.% Distinguish et$een asorption and assimilation
,bsorption: The movement of a fluid or dissolved su#stances across a mem#rane ,ssimilation: The conversion of nutrients into fluid or solid parts of an organism 7int= A#sorption is taing it into something assimilation is maing it a part of something %.1.( &'plain ho$ the structure of the villus is related to its role in asorption and transport of products of digestion icrovilli:
in)le epithelial layer: nsures minimal diffusion distance #et%een the intestinal lumen and capillary net%or acteals: A#sor# lipids from the intestine into the lymphatic system (%hich are later rea#sor#ed #ac into normal circulation) ntestinal crypts: 'ocated #et%een villi and release $uices that act as a carrier fluid for nutrients embrane proteins ; mitochondria: ,igh amounts to ena#le active transport into cells (contents then passively diffuse into #loodstream)
&eatures of a 5illus
%.2.1 Dra$ and lael a diagram of the heart sho$ing the four chamers, associated lood vessels, valves and the route of the lood through the heart 5alves and irection of 7lood &lo% ,eart Cham#ers and 5essels
%.2.2 State that coronary arteries supply heart muscle $ith o'ygen and nutrients The heart is a muscle that must continually contract in order to pump #lood around the #ody Coronary arteries form a net%or of vessels around the heart and supply the cardiac tissue %ith oygen and nutrients (i.e. glucose) These are re=uired to produce the necessary energy via aero#ic respiration - if a coronary artery is #loced a heart attac may occur %.2.3 &'plain the action of the heart in terms of collecting lood, pumping lood and opening and closing valves 7lood returning from all parts of the #ody (ecept lungs) enter the right atrium via the vena cava - this #lood is relatively deoygenated The #lood passes from the right atrium to the right ventricle and then via the pulmonary artery to the lungs (%here #lood is reoygenated) The #lood returns to the left atrium via the pulmonary vein and passes through the left ventricle to the aorta %here it is pumped around the #ody
The heart valves maintain the one-%ay flo% of #lood:
hen the atria contract atrioventricular (A5) valves open 7lood flo%s from the atria and into the ventricles hen the ventricles contract the A5 valves close and semilunar valves
open
This forces #lood out of the ventricles and into the arteries As arterial pressure rises the semilunar valves close ensuring the one%ay flo% of #lood %.2.4 Outline the control of the hearteat in terms of myogenic muscle contraction, the role of the pacema!er, nerves, the medulla of the rain and epinephrine adrenalineThe contraction of the heart tissue (myocardium) is myogenic meaning the signal for cardial contraction arises %ithin the heart muscle itself ithin the %all of the right atrium are a specialised pleus of nerves called the sinoatrial node (;A) The sinoatrial node initiates contraction of the cardiace muscle and acts as a pacemaer regulating normal sinus rhythm ?t stimulates atria to contract and %hen ecitation reaches the $unction #et%een atria and ventricles stimulates another node (atrioventicular node) The atrioventricular node (A5) sends signals via the 7undle of ,is to +urin$e fi#res %hich cause ventricular contraction This se=uence al%ays ensures their is a delay #et%een atrial and ventricular contractions resulting in t%o heart sounds ("lu# du#")
!yogenic Control of the ,eart 7eat
The pacemaer is under autonomic control from the #rain specifically the medulla o#longata (#rain stem)
;ympathetic nerves speed up heart rate #y releasing a neurotransmitter (noradrenaline) to increase the rate of myocardial contraction +arasympathetic nerves splo% do%n heart rate #y releasing a neurotransmitter (acetylcholine) to decrease the rate of myocardial contraction Additionally the heart rate may #e increased #y the chemical release of the hormone adrenaline into the #lood (from the adrenal gland) %.2.# &'plain the relationship et$een the structure and function of arteries, capillaries and veins ,rteries Arteries carry #lood at high pressure (B6 - 126 mm ,g) They have a narro%er lumen (to maintain high pressure) surround #y a thic %all made of t%o layers The middle layer (tunica media) contains muscle and elastin to help maintain pulse flo% (it can contract and stretch) The outer layer (tunica adventitia) contains collagen prevents the artery rupturing due to the high pressure #lood flo% 9eins
5eins carry #lood under lo% pressure (916 mm ,g) They have a very %ide lumen (eeps pressure lo% and allo%s greater flo% of #lood) The %alls of tissue surrounding the vein are thin (#lood is not travelling in rhythmic pulses) They have valves to prevent #lood pooling at etremities (arteries do not have valves) Capillaries Capillaries are involved %ith material and gas echange %ith the surrounding #ody tissue 7lood pressure in the capillaries is relatively lo% (J14 mm ,g) and they have a very small diameter (J4 micrometers %ide) Their %all is made up a a single layer of cells to allo% for ease of diffusion Capillaries may contain pores to aid the transport of material
;tructure of 7lood 5essels
%.2.% State that lood is composed of plasma, erythrocytes, leu!ocytes phagocytes and lymphocytes- and platelets There are four main components to #lood: +lasma - the fluid medium of the #lood rythrocytes - red #lood cells (involved in oygen transport) 'euocytes - %hite #lood cells such as phagocytes (non-specific immunity) and lymphocytes (specific immunity) +latelets - responsi#le for #lood clotting (haemostasis) %.2.( State that the follo$ing are transported y lood= nutrients, o'ygen, caron dio'ide, hormones, antiodies, urea and heat The follo%ing things are transported #y #lood:
utrients (e.g. glucose)
nti#odies
ar#on dioide
ormones
ygen
rea
eat (not a molecules unlie all the others) %.3.1 Define pathogen A pathogen is a disease-causing micro-organism virus or prion %.3.2 &'plain $hy antiiotics are effective against acteria ut not against viruses Anti#iotics are su#stances or compounds that ill or inhi#it the gro%th of #acteria #y targeting the meta#olic path%ays of proaryotes ;pecific proaryotic features that may #e targeted #y anti#iotics include ey en0ymes /6; ri#osomes and the #acterial cell %all 7ecause euaryotic cells do not have these features anti#iotic can ill #acterial cells %ithout harming humans (or viruses)
5irus do not carry out meta#olic reactions themselves #ut instead infect host cells and tae over their cellular machinery 5iruses need to #e treated %ith specific antiviral agents that target features specific to viruses (e.g. reverse transcriptase in retroviruses)
The first line of defence against infection are the surface #arriers that prevent the entry of pathogenic su#stances These surface #arriers include the sin and mucous mem#ranes ;ummary of ;urface 7arriers
%.3.3 Outline the role of s!in and mucous memranes in defence against pathogens S"in +rotects eternal structures (outer #ody areas) A dry thic and tough region made of predominantly dead surface cells Contains #iochemical defence agents (se#aceous glands secrete chemicals %hich inhi#it the gro%th of some #acteria) The sin also releases acidic secretions to lo%er p, and prevent #acteria from gro%ing Mucous membranes +rotect internal structures (eternally accessa#le cavities and tu#es such as trachea vagina and urethra) A thin region containing living surface cells that release fluids to %ash a%ay pathogens (mucus tears saliva etc.) Contains #iochemical defence agents (secretions contain lyso0yme %hich can destroy cell %alls and cause cell lysis) !ucous mem#ranes may #e ciliated to aid in the removal of pathogens (along %ith physical actions such as coughing or snee0ing)
The second line of defence against pathogenic invasion are the non-specific defence mechanisms on-specific mechanisms do not differentiate #et%een types of microorganisms and al%ays invoe the same response
amples of non-specific defence mechanisms include phagocytic leucocytes inflammation fever and anti-micro#ial proteins on-specific ?mmunity
%.3.4 Outline ho$ phagocytic leucocytes ingest pathogens in the lood and in ody tissue +hagocytic leucocytes (macrophages) circulate in the #lood #ut may move into #ody tissue (etravasation) in response to infection They concentrate at sites of infection due to the release of chemicals (such as histamine) from damaged #ody cells +athogens are engulfed %hen cellular etensions (pseudopodia) surround the pathogen and then fuse se=uestering it in an internal vesicle The vesicle may then fuse %ith the lysosome to digest the pathogen ;ome of the pathogens antigenic fragments may #e presented on the surface of the macrophage in order to help stimulate anti#ody production This mechanism of endocytosis is called phagocytosis ("cell-eating")
8vervie% of +hagocytosis #y a 'eucocyte
The third line of defence are the specific defences coordinated #y a type of leucocyte called lymphocytes These can recognise and respond specifically to different types of microorganism and have memory (can respond more effectively upon reinfection) ;pecific ?mmunity
%.3.# Distinguish et$een antigens and antiodies ,nti)en: A su#stance that the #ody recognises as foreign and that can evoe an immune response ,ntibody: A protein produced #y certain %hite #lood cells (7 lymphocytes plasma cells) in response to an antigen
Anti#odies are made Anti#odies made up of of polypeptide polypeptide chains chains (2 light and and 2 heavy chains) $oined together #y disulphide #onds to form a K-shaped molecule The ends of the arms are %here the antigens #ind and these areas are called the varia#le regions as these %ill differ #et%een anti#odies ach type of anti#ody %ill recognise a uni=ue antigenic fragment maing this interaction specific (lie en0yme-su#strate interactions) ;tructure of a
%.3.% &'plain antiody production 7 lymphocytes (7 cells) are anti#ody-producing cells that develop in the #one marro% to produce a highly specific anti#ody that recognises one type of antigen hen %andering macrophages encounter a pathogen they digest it and present the antigenic fragments on their surface to helper T lymphocytes (T, cells) These cells activate the appropriate 7 cell %hich divides and differentiates into short-lived plasma cells that produce massive =uantities of anti#ody (J2666 molecules per second for J - 4 days) A small proportion proportion of 7 cell clones develop develop into into memory cells %hich %hich may survive for years providing long-term immunity %.3.( Outline the effect of 7"> on the immune system system The human immunodeficiency virus (,?5) is a retrovirus that infects helper T lymphcytes (T , cells) *everse transciptase allo%s viral A to #e produced from its *A code %hich is integrated into the host cells genome
After a num#er num#er of years of inactivity (during %hich infected infected T , cells have continually reproduced) the virus #ecomes active and #egins to spread destroying the T , cells in the process (no%n as the lysogenic cycle) This results in lo%er immunity as anti#ody production is compromised the individual is no% suscepti#le to opportunistic infections Timeline of ,?5 ?nfection
%.3.) Discuss the cause, transmission and social implications of "DS "DS Cause Ac=uired Ac=uire d ?mmunodeficieny ?mmunodeficieny ;yndrome (A?;) is is a collection collection of symptoms symptoms and infections caused #y the destruction of the immune system #y ,?5 hile ,?5 infection results in a lo%ering in immunity over a num#er of years A?; descri#es the final stages %hen o#serva#le symptoms develop Transmission ,?5 is transmitted through the echange of #odily fluids (including unprotected se #lood transfusions #reast feeding child #irth etc.) The ris of eposure to ,?5 through seual contact can #e reduced #y using late protection (condoms) A minority of of people people are immune immune to ,?5 ,?5 infection infection (they do not have have the CH T cell receptor that ,?5 needs to infect the cell) Social 1mplications +eople %ith ,?5 may #e stigmatised and discriminated against potentially leading to unemployment and poverty !a$ority of people %ho die from A?; are at a productive age %hich may cripple a country"s %orforce and economic gro%th ?t can result in an increased num#er of orphans taing a country"s %elfare resources +overty may increase transmission of A?; (due to poor education and high cost of treatments) creating a moral o#ligation for assistance from %ealthier countries %.4.1 Distinguish et$een ventilation, gas e'change and cell respiration *espiration is the transport of oygen to cells %here energy production taes place and involves three ey processes: air #et%een the lungs and the atmosphere@ 9entilation: The echange of air it is achieved #y the physical act of #reathing -as exchan)e: The echange of oygen and car#on dioide in the alveoli and the #loodstream@ it occurs passively via diffusion Cell Respiration: The release of AT+ from organic molecules@ it is greatly enhanced #y the presence of oygen (aero#ic respiration) %.4.2 &'plain the need for a ventilation system
7ecause gas echange is a passive process a ventilation system is needed to maintain a concentration gradient %ithin the alveoli 8ygen is needed #y cells to mae AT+ via aero#ic respiration %hile car#on dioide is a %aste product of this process and must #e removed Therefore oygen must diffuse from the lungs into the #lood %hile car#on dioide must diffuse from the #lood into the lungs This re=uires a high concentration of oygen - and a lo% concentration of car#on dioide - in the lungs A ventilat ventilation ion system system maintains maintains this concentra concentration tion gradient gradient #y continual continually ly cycling the air in the lungs %ith the atmosphere %.4.3 Descrie the features of alveoli that adapt them to gas e'change hin wall: !ade of a single layer of flattened cells so that diffusion distance is small ich capillary networ": Alveoli are covered #y a dense net%or of capillaries that help to maintain a concentration gradient ncreased S,:9o S ,:9oll ratio: ,igh num#ers of spherically-shaped alveoli optimise surface area for gas echange (G66 million alveoli B6 m 2) oist: ;ome cells in the lining secrete fluid to allo% gases to dissolve and to prevent alveoli from collapsing (through cohesion) %.4.4 Dra$ an lael a diagram of the ventilation ventilation system, including trachea, lungs, ronchi, ronchioles and alveoli The 2uman 9entilation System
%.4.# &'plain the mechanism of ventilation of the the lungs in terms of volume and pressure changes caused y the internal and e'ternal intercostal muscles, the diaphragm and adominal muscles
7reathing is the active movement of respiratory muscles that ena#le the passage of air to and from the lungs The mechanism of #reathing is descri#ed as negative pressure #reathing as it is driven #y the creation of a negative pressure vacuum %ithin the lungs according to 7oyle"s 'a% (pressure is inversely proportional to volume)
1nspiration iaphragm muscles contract and flatten do%n%ards ternal intercostal muscles contract pulling ri#s up%ards and out%ards This increases the volume of the thoracic cavity (and therefore lung volume) The pressure of air in the lungs is decreased #elo% atmospheric pressure Air flo%s into the lungs to e=ualise the pressure
Expiration iaphragm muscles rela and diphragm curves up%ards A#dominal muscles contract pushing diaphragm up%ards ternal intercostal muscles rela allo%ing the ri#s to fall ?nternal intercostal muscles contract pulling ri#s do%n%ards This decreases the volume of the thoracic cavity (and therefore lung volume) The pressure of air in the lungs is increased a#ove atmospheric pressure Air flo%s out of the lungs to e=ualise the pressure %.#.1 State that the nervous system consists of the central nervous system CS- and peripheral nerves, and is composed of cells called neurons that carry rapid electrical impulses eurons are cells that are specialised for the conduction of nerve impulses and serve as the fundamental unit of the nervous system The nervous system can #e divided into t%o main parts: Central Nervous System *CNS+: !ade up of the #rain and the spinal cord !eripheral Nervous System *!NS+: !ade of peripheral nerves %hich lin the C; %ith the #ody"s receptors and effectors %.#.2 Dra$ and lael a diagram of the structure of the motor neuron
%.#.3 State that nerve impulses are conducted from receptors to the CS y sensory neurons, $ithin the CS y relay neurons, and from the CS to effectors y motor neurons There are three main types of neurons in the nervous system: Sensory Neurons: Conduct nerve impulses from receptors to the C; (afferent path%ay) Relay Neurons: Conduct nerve impulses %ithin the C; (also called interneurons or connector neurons) Motor Neurons: Conduct nerve impulses from the C; to effectors (efferent path%ay)
The ;timulus-*esponse +ath%ay
%.#.4 Define resting potential and action potential depolarisation and repolarisationRestin) !otential: The charge difference across the mem#rane %hen a neuron is not firing (-/6 m5) as maintained #y the sodium-potassium pump ,ction !otential: The charge difference across the mem#rane %hen a neuron is firing (a#out 36 m5) %epolarisation: The change from a negative resting potential to a positive action potential (caused #y opening of sodium channels) Repolarisation: The change from a positive action potential #ac to a negative resting potential (caused #y opening of potassium channels)
%.#.# &'plain ho$ a nerve impulse passes along a non5myelinated neuron -eneration o a Restin) !otential The sodium-potassium pump (a HLH pump) maintains the electrochemical gradient of the resting potential (-/6 m5) ?t is a transmem#rane protein that uses active transport to echange a H and LH ions across the mem#rane (antiport mechanism) ?t epels 3 a H ions for every 2 L H ions admitted (in addition some of the LH ions %ill lea #ac out of the cell)
This maes the inside of the mem#rane relatively negative %hen compared to the outside (-/6 m5 resting potential) Transmission o an ,ction !otential ;odium and potassium channels in nerve cells are voltage-gated meaning they can open and close depending on the voltage across the mem#rane ?n response to a signal at a sensory receptor or dendrite sodium channels open and sodium enters the neuron passively The influ of sodium (a H in) causes the mem#rane potential to #ecome positive (depolarisation) ?f a sufficient change in mem#rane potential is achieved (threshold potential) ad$acent voltage-gated sodium channels open generating a %ave of depolarisation (action potential) that spreads do%n the aon The change in mem#rane potential also activates voltage-gated potassium channels causing potassium to eit the neuron passively The efflu of potassium (L H out) causes the mem#rane potential to #ecome negative again (repolarisation) 7efore the neuron can fire again the original distri#ution of ions (a H out LH in) must #e re-esta#lished #y the a HLH pump The ina#ility to propagate another action potential during this time (refractory period) ensures nerve impulses only travel in one direction
;altatory Conduction
%.#.% &'plain the principles of synaptic transfer The $unction #et%een t%o neurons is called a synapse it forms a physical gap #et%een the pre-synaptic and post-synaptic neurons An action potential (electrical signal) cannot cross the synaptic gap so it triggers the release of chemicals (neurotransmitters) to continue the signal Chemical Transer ,cross Synapses hen an action potential reaches the aon terminal it triggers the opening of voltage-gated calcium channels Calcium ions (Ca 2H) diffuse into the cell and promote the fusion of vesicles (containing neurotransmitters) %ith the plasma mem#rane The neurotransmitters are released from the aon terminal #y eocytosis and cross the synaptic cleft eurotransmitters #ind to appropriate neuroreceptors on the post-synaptic mem#rane opening ligand-gated channels citatory neurotransmitters (e.g. noradrenaline) open ligand-gated sodium channels (depolarisation) ?nhi#itory neurotransmitters (e.g.
8vervie% of ;ynaptic Transfer
%.#.( State that the endocrine system consists of glands that release hormones that are transported in the lood An endocrine gland is a ductless gland in the #ody that manufactures chemical messengers called hormones and secretes them directly into the #lood ,ormones act on distant sites (target cells) and tend to control slo% long-term activities such as gro%th and seual development
ndocrine ;ystem %.#.) State that homeostasis involves maintaining the internal environment et$een limits, including lood p7, caron dio'ide concentration, lood glucose concentration, ody temperature and $ater alance ,omeostasis is the tendency of an organism or cell to maintain a constant internal environment %ithin tolerance limits ?nternal e=uili#rium is maintained #y ad$usting physiological processes including:
7ody temperature (normally 3G - 3B IC) 7lood p, (normally /.34 - /.4) Car#on dioide concentration (normally 34 - 4 mm,g) 7lood glucose concentration (normally /4 - E4 mg d') ater #alance (varies %ith individual #ody si0e) %.#.* &'plain that homeostasis involves monitoring levels of variales and correcting changes in levels y negative feedac! mechanisms !ost homeostatic control mechanisms operate through a negative feed#ac loop hen specialised receptors detect a change in an internal condition the response generated %ill #e the opposite of the change that occurred hen levels have returned to e=uili#rium the effector ceases to generate a response ?f levels go too far in the opposite direction antagonistic path%ays %ill #e activated to restore the internal #alance
egative &eed#ac 'oop
%.#.1+ &'plain the control of ody temperature, including the transfer of heat in lood, and the roles of the hypothalamus, s$eat glands, s!in arterioles and shivering Animals capa#le of temperature regulation %ithin a given range are called homeotherms and maintain a constant #ody temperature through a negative feed#ac loop The hypothalalmus acts as a control centre in thermoregulation #y detecting fluctuations in #ody temperature The sin also possesses thermoreceptors and relays this information to the hypothalamus %hich coordinates corrective measures
hen #ody temperature rises the follo%ing cooling mechanisms may occur: 9asodilation: The sin arterioles dilate #ringing #lood into closer proimity to the #ody surface and allo%ing for heat transfer (convective cooling) Sweatin): ;%eat glands release s%eat %hich %hich is evaporated at the cost of latent heat in the air thus cooling the #ody (evaporative cooling) hen #ody temperature falls the follo%ing heating mechanisms may occur: 9asoconstriction: The sin arterioles constrict moving #lood a%ay from the surface of the #ody thus retaining the heat carried %ithin the #lood Shiverin): !uscles #egin to shae in small movements epending energy through cell respiration (%hich produces heat as a #y-product) 8ther mechanisms through %hich homeotherms may regulate their #ody temperature include:
!iloerection: Animals %ith furry coats can mae their hair stand on end (piloerection) trapping pocets of %arm air close to the #ody surface #ehavioural responses: Animals may physically respond to environmental conditions in a #id to regulate temperature (e.g. #athing #urro%ing etc.)
Thermoregulation #y the ervous ;ystem
%.#.11 &'plain the control of lood glucose concentration, including the roles of glucagon, insulin and the alpha and eta cells in the pancreatic islets The #ody re=uires volumes of glucose in order to mae AT+ ho%ever the amount of AT+ demand %ill fluctuate according to need and thus the #ody regulates its release of glucose into the #loodstream as high levels of glucose in the #loodstream can damage cells (creates hypertonicity) T%o hormones insulin and glucagon are responsi#le for controlling #lood glucose concentration (they have antagonistic functions) These hormones are released from different groups of cells %ith pancreatic pits (called the islets of 'angerhans) and act principally on the liver
hen #lood glucose levels are high (e.g. after feeding): ?nsulin is released from #eta cells in the pancreas and causes a decrease in #lood glucose concentration This may involve stimulating glycogen synthesis in the liver (glycogenesis) promoting glucose uptae into the liver and adipose tissue or increasing the rate of glucose #reado%n (increase cell respiration) hen #lood glucose levels are lo% (e.g. after strenuous eercise):
This may involve stimulating glycogen #reado%n in the liver (glycogenolysis) promoting glucose release from the liver and adipose tissue or decreasing the rate of glucose #reado%n (decrease cell respiration) 7lood
%.#.12 Distinguish et$een type " and type "" diaetes
%.%.1 Dra$ and lael diagrams of the adult male and female reproductive systems Male Reproductive System
;ide 5ie% &ront 5ie% (emale Reproductive System
;ide 5ie% &ront 5ie% %.%.2 Outline the role of hormones in the menstrual cycle, including ?S7 follicle stimulating hormone-, /7 luteinising hormone-, estrogen and progesterone
%.%.3 nnotate a graph sho$ing hormone levels in the menstrual cycle, illustrating the relationship et$een changes in hormone levels and ovulation, menstruation and the thic!ening of the endometrium
(ollicular !hase: &;, stimulates gro%th of several follicles ominant follicle secretes estrogen strogen inhi#its gro%th of other follicles (and &;,) strogen stimulates development of endometrium 0vulation: A surge in ', causes ovulation (egg release) *upturing of follicle creates a corpus luteum
.uteal !hase: Corpus luteum secretes progesterone (and estrogen) +rogesterone stimulates development of endometrium strogen and progesterone inhi#it &;, and ', Corpus luteum degrades over time hen corpus luteum degrades progesterone levels drop ithout progesterone endometrium cannot #e maintained ndometrium is sloughed a%ay (menstruation) o longer inhi#ited &;, can start menstrual cycle again
?f fertilisation of egg occurs the 0ygote releases a hormone (hC<) %hich maintains the corpus luteum
%.%.4 /ist three roles of testosterone in males +re-natal development of male genitalia evelopment of secondary se characteristics !aintenance of se drive (li#ido) %.%.# Outline the process of in vitro fertilisation ?n vitro fertilisation refers to fertilisation that occurs outside the #ody ("in vitro" "in glass")
top normal menstrual cycle (%ith drugs) ormone treatments to develop follicles (&;, to stimulate follicle gro%th @ hC< for follicle maturation) xtract multiple e))s from ovaries perm selected prepared (capacitation) and then in$ected into egg via intra-cytoplasmic sperm in$ection (?C;?) ertilisation occurs under controlled conditions (in vitro) mplantation of multiple em#ryos into uterus est or pre)nancy is conducted to see if implantation %as successful
?n 5itro &ertilisation
