Q.1.Which statement regarding the differences between electron microscopy and light microscopy is false? a. Images produced by electron microscopes are always black and white. b. The higher resolution of electron microscopes is due to the fact that the wavelength by electrons is about one hundred thousand (1 x 105) times longer than the wavelength of visible light. c. Viruses and other objects smaller than about 200 nm (0.2 µm) must be examined via electron microscopy. d. Instead of using glass lenses, an electron microscope uses electromagnetic lenses. Q.2.Which of the following statements regarding resolution is true? A. In order to achieve high magnification with good resolution, a small objective lens must be used. b. The white light used in a compound light microscope has a relatively short wavelength in order to resolve structures smaller than 0.002 µm. c. A general principle of microscopy is that the shorter the wavelength of light used in the instrument, the lower the resolution. d. Resolution (resolving power) is calculated by multiplying the objective lens power by the ocular lens power. Q.3.Which instrument would be used to examine living cells that are attached to other surfaces, such as artery plaques? a. Phase-contrast microscope b. Scanning acoustic microscope c. Fluorescence microscope d. Confocal microscope Q.4.For viewing which of the following would a scanning electron microscope not be the instrument of choice? a. The complexity of T-even bacteriophages b. The helical structure of deoxyribonucleic acid (DNA) c. Human erythrocytes (red blood cells) d. E. coli bacteria Q.5.Which of the following describes the correct path of light in a compound light microscope, from the illumination source to the eye of the observer? a. Condenser lenses → prism → specimen → objective lenses → body tube → ocular lens → eye b. Ocular lens → body tube → condenser lens → specimen → objective lens → prism → eye c. Objective lenses → specimen → condenser lenses → body tube → prism → ocular lens → e ye d. Condenser Condenser lenses → specimen → objective lenses → body tube → prism → ocular lens → e ye Why do electron microscopes have higher resolving power than light microscopes?
a. The fluorescent screen adds another magnification step. b. They are capable of producing 3-dimensional images, which light microscopes cannot do. c. Electrons have a smaller wavelength than visible light, leading to higher resolution. d. The copper grid used in electron microscopy provides enhanced resolution. c. Electrons have a smaller wavelength than visible light, leading to higher resolution Which of the following is a lens found on electron microscopes but not on light microscopes? a. Objective lens b Projector lens c. Condenser lens d. Eyepiece lens b Projector lens Which type of microscope would allow the viewer to see ribosomes inside a cell? a. A light microscope, transmission electron microscope, and scanning electron microscope can all view ribosomes inside a cell. b. A light microscope c. A transmission electron microscope d. A scanning electron microscope c. A transmission electron microscope Which of the following is a characteristic shared by both electron and light microscopes? a. They both employ the use of objective lenses. b. Both microscopes require an internal camera to visualize the specimen. c. Both microscopes have a resolving power of 0.01 nm. d. They both utilize white light to magnify the specimen. a. They both employ the use of objective lenses. What is the fate of the electrons that interact with a specimen in an electron microscope? a. They are reflected by the specimen. b. They are refracted by the specimen. c. They may be absorbed, reflected, or refracted by the specimen. d. They are absorbed by the specimen c. They may be absorbed, reflected, or refracted by the specimen. What is the role of lenses in microscopy? a. Lenses focus either light or electrons to create a magnified image of a specimen. b. Lenses are only used to magnify specimens that are smaller than whole red blood cells. c. Lenses increase the contrast to determine structural differences in stained specimens. a. Lenses focus either light or electrons to create a magnified image of a specimen. Scanning electron microscopy (SEM) ________.
a. can be used to view biomolecules at the atomic level b. requires no special treatment of the specimen c. provides a three-dimensional image of a cell's surface d. is used to view internal cellular structure c. provides a three-dimensional image of a cell's surface In which type of microscopy do the specimens appear to be three-dimensional (3-D), allowing their external features to be viewed best? a. Scanning electron microscopy (SEM) b. Transmission electron microscopy (TEM) c. Phase-contrast microscopy d. Darkfield microscopy a. Scanning electron microscopy (SEM) If a bacterial smear were stained with a blue basic stain, then counterstained with a red acidic stain, one would expect to see ________. a. Red cells against a blue background b. Blue cells against a red background c. Red and blue cells against a colorless background d. Red acid-fast cells b. Blue cells against a red background In the decolorizing step of the Gram stain, which reagent is used? a. Alcohol-acetone b. Malachite green c. Iodine d. Crystal violet a. Alcohol-acetone What is the purpose of safranin in the Gram stain technique? a. It is a counterstain, which will make gram-positive bacteria colorless. b. It is a decolorizing agent. c. It is the primary stain used to impart a pink color to all cells in a heat-fixed smear. d. It is a counterstain, which turns gram-negative bacteria pink. d. It is a counterstain, which turns gramnegative bacteria pink. A simple stain ________. a. readily differentiates microbial groups b. allows observation of bacterial motility c. improves the contrast between the cell and the background, thus improving the visibility of bacterial cell shapes and structures d. requires two steps: a staining step, then the addition of a mordant to decolorize the specimen c. improves the contrast between the cell and the background, thus improving the visibility of bacterial cell shapes and structures Regarding the Gram stain technique, which of the following is the primary stain? a. Crystal violet b. Safranin c. Iodine
d. Carbolfuchsin a. Crystal violet While staining a mixed culture of Gram-positive and Gram-negative bacteria, switching the order of steps 2 and 3 would result in ______________________. a. all bacteria appearing purple b. all bacteria appearing clear c. all bacteria appearing pink d. a change in the Gram reaction; Gram-negative cells would appear purple while Gram-positive cells would appear pink. c. all bacteria appearing pink Which structural feature of Gram-positive bacteria enhances their ability to retain the crystal violet dye? a. an outer membrane b. a thin peptidoglycan layer c. a thick peptidoglycan layer d. All of the above contribute to a Gram-positive cell's ability to retain crystal violet. c. a thick peptidoglycan layer What would you anticipate seeing if you accidentally switched crystal violet and safranin while performing a Gram stain? a. All bacteria would appear purple. b. Gram-positive bacteria would appear pink and Gram-negative bacteria would appear purple. c. Gram-positive bacteria would appear purple and Gram-negative bacteria would appear pink. d. All bacteria would appear pink. a. All bacteria would appear purple. What would you expect to see if you forgot to perform step 2 of the Gram stain procedure? a. Gram-positive cells would appear purple and Gramnegative cells would appear pink. b. All bacteria would appear pink. c. Gram-positive cells would appear pink and Gramnegative cells would appear purple. d. All bacteria would appear purple. b. All bacteria would appear pink. You find colorless areas in cells in a Gram-stained smear. What should you do next? a. A capsule stain b. A simple stain c. A flagella stain d. An endospore stain e. An acid-fast stain d. An endospore stain The purpose of a mordant in the Gram stain is a. To make the flagella visible. b. To remove the simple stain. c. To make gram-negative cells visible. d. To make the bacterial cells larger. e. To prevent the crystal violet from leaving the cells. e. To prevent the crystal violet from leaving the cells.
You suspect a 100-nm structure is present in a cell. Which of the following provides the lowest magnification that you can use to see this structure? a. Transmission electron microscope b. Phase-contrast microscope c. Scanning electron microscope d. Brightfield microscope e. Darkfield microscope c. Scanning electron microscope Which microscope is used to see internal structures of cells in a natural state? a. Phase-contrast microscope b. Compound light microscope c. Electron microscope d. Fluorescence microscope w. Darkfield microscope a. Phase-contrast microscope The counterstain in the Gram stain is a. A negative stain. b. A mordant. c. An acid dye. d. A basic dye. e. Necessary to determine the Gram reaction. d. A basic dye. Which microscope can be used to visualize DNA or botulinum toxin? a. Compound light microscope b. Scanning tunneling microscope c. Scanning electron microscope d. Phase-contrast microscope e. Confocal microscope b. Scanning tunneling microscope Cells are differentiated after which step in the Gram stain? a. Alcohol-acetone b. Iodine c. Crystal violet d. Safranin a. Alcohol-acetone The counterstain in the acid-fast stain is a. A basic dye. b. A negative stain. c. An acid dye. d. A mordant. e. Necessary to determine acid-fast cells. a. A basic dye. Which of the following microscopes uses visible light? a. Scanning electron microscope b. Confocal microscope c. Scanning acoustic microscope d. DIC e. Fluorescence microscope d. DIC The appearance of gram-negative bacteria after addition of the mordant in the Gram stain. a. Purple
b. Red c. Colorless d. Brown a. Purple Which microscope takes advantage of differences in the refractive indexes of cell structures? a. Fluorescence microscope b. Compound light microscope c. Phase-contrast microscope d. Darkfield microscope e. Electron microscope c. Phase-contrast microscope In which microscope does the image look like a negative stain? a. Fluorescence microscope b. Scanning acoustic microscope c. Darkfield microscope d. Phase-contrast microscope e. Two-photon microscope c. Darkfield microscope Assume you stain Bacillus by applying malachite green with heat and then counterstaining with safranin. Through the microscope, the green structures are a. Flagella. b. Cell walls. c. Capsules. d. Endospores. e. Can't tell d. Endospores. What structure does light pass through after leaving the condenser in a compound light microscope? a. Objective lens b. Illuminator c. Ocular lens d. Specimen d. Specimen Which microscope is used to see intracellular detail in a living cell? a. Two-photon microscope b. Transmission electron microscope c. Brightfield microscope d. Fluorescence microscope e. Atomic force microscope a. Two-photon microscope The appearance of gram-negative bacteria after completing the Gram stain. a. Purple b. Red c. Colorless d. Brown b. Red What Gram reaction do you expect from acid-fast bacteria? a. Gram-negative b. Gram-positive c. Both gram-positive and gram-negative d. Can't tell b. Gram-positive
The resolution of a microscope can be improved by changing the a. Fine adjustment. b. Wavelength of light. c. Coarse adjustment. d. Condenser. e. Diaphragm. b. Wavelength of light. Place the following steps in the correct sequence: 1-Staining; 2-Making a smear; 3-Fixing. a. 1-2-3 b. 2-3-1 c. 1-3-2 d. The order doesn't matter e. 3-2-1 b. 2-3-1 In this microscope, the observer does NOT look at an image through a lens. a. Compound light microscope b. Phase-contrast microscope c. Darkfield microscope d. Fluorescence microscope e. Electron microscope e. Electron microscope Bacterial smears are fixed before staining to a. make their walls permeable. b. affix the cells to the slide. c. accept stain. d. kill the bacteria and affix the cells to the slide. e. kill the bacteria. d. kill the bacteria and affix the cells to the slide. The appearance of gram-negative bacteria after addition of the decolorizing agent in the Gram stain. a. Purple b. Red c. Colorless d. Brown c. Colorless Which microscope is used to see detail of a 300-nm virus? a. DIC microscope b. Phase-contrast microscope c. Electron microscope d. Fluorescence microscope e. Darkfield microscope c. Electron microscope The best use of a negative stain is a. to determine Gram reaction. b. to determine cell shape. c. to see endospores. d. to determine cell size. e. to determine cell size and shape. e. to determine cell size and shape. Simple staining is often necessary to improve contrast in this microscope. a. Darkfield microscope b. Electron microscope c. Phase-contrast microscope d. Fluorescence microscope
e. Compound light microscope e. Compound light microscope The purpose of the ocular lens is to a. Magnify the image from the objective lens. b. Decrease the light. c. Improve resolution. d. Increase the light. e. Decrease the refractive index. a. Magnify the image from the objective lens. Place the steps of the Gram stain in the correct order: 1-Alcohol-acetone; 2-Crystal violet; 3-Safranin; 4Iodine. a. 1-2-3-4 b. 2-1-4-3 c. 4-3-2-1 d. 2-4-1-3 e. 1-3-2-4 d. 2-4-1-3 Which microscope is most useful for visualizing a biofilm? a. Atomic force microscope b. Compound light microscope c. Transmission electron microscope d. Phase-contrast microscope e. Scanning acoustic microscope e. Scanning acoustic microscope The appearance of gram-positive bacteria after addition of the first dye in the Gram stain. a. Purple b. Red c. Colorless d. Brown a. Purple Which microscope uses two beams of light to produce a three-dimensional, color image? a. Darkfield microscope b. Electron microscope c. Phase-contrast microscope d. DIC microscope e. Fluorescence microscope d. DIC microscope Which microscope achieves the highest magnification and greatest resolution? a. Compound light microscope b. Phase-contrast microscope c. Darkfield microscope d. Fluorescence microscope e. Electron microscope e. Electron microscope This microscope produces an image of a light cell against a dark background; internal structures are NOT visible. a. Compound light microscope b. Phase-contrast microscope c. Darkfield microscope d. Fluorescence microscope e. Electron microscope c. Darkfield microscope
Which microscope is used to observe a specimen that emits light when illuminated with an ultraviolet light? a. Phase-contrast microscope b. Darkfield microscope c. Fluorescence microscope d. Compound light microscope e. Electron microscope c. Fluorescence microscope The appearance of gram-positive bacteria after adding the counterstain in the Gram stain. a. Purple b. Red c. Colorless d. Brown a. Purple Van Leeuwenhoek's microscope magnified up to 300x. This was a(n) a. Compound microscope. b. Electron microscope. c. Simple microscope. d. Confocal microscope. e. Phase-contrast microscope. c. Simple microscope. What is the total magnification of a chloroplast viewed with a 10x ocular lens and a 45x objective lens? a. 10x b. 4.5x c. 450x d. 100x e. 45x
