BIO 235 Microbiology Exam TEST 1()

BIO 235 Microbiology Exam TEST 1() units of measurement - CORRECT ANSWER1 µm = 10-6 m = 10-3 mm 1 nm = 10-9 m = 10-6 mm 1000 nm = 1 µm 0.001 µm = 1 nm total magnification (compound microscopes) - CORRECT ANSWER-the image from the objective lens is magnified again by the ocular lens -total magnification = objective lens x ocular lens resolution - CORRECT ANSWER-the ability of the lenses to distinguish two points. -shorter wavelengths of light provide greater resolution objective lens - CORRECT ANSWERlens closest to the specimen condenser - CORRECT ANSWERfocuses light onto the specimen brightfield illumination microscopy - CORRECT ANSWER-dark objects are visible against a bright background -light reflected off the specimen does not enter the objective lens -used for stained microbial cells darkfield illumination microscopy - CORRECT ANSWER-light objects are visible against a dark background -light reflected off the specimen enters the objective lens -used for cells that do not stain easily phase contrast microscopy - CORRECT ANSWER-accentuates the diffraction of a light that passes through a specimen -to facilitate detailed examination of the internal structures of living specimens DI contrast microscopy - CORRECT ANSWER-differential interference -uses a polarizer to create two distinct beams of polarized light -typically used on unstained cells to reveal internal structures -gives structures such as nucleus, endospores, vacuoles, and granules a three-dimensional appearance fluorescence microscopy - CORRECT ANSWER-used to visualize specimens that fluoresce, emitting light of one color after absorbing light of different color -some cells naturally fluoresce due to components like chlorophyll, but others have to be stained with a fluorescent dye -often rapidly used to detect and identify microbes in tissues or clinical specimens as well as for enumerating bacteria in a natural environment confocal scanning laser microscopy - CORRECT ANSWER-uses a computerized microscope coupled with a laser source to generate a 3D image -computer can focus the laser on single layers of the specimen -different layers can then be compiled for a 3D image TEM - CORRECT ANSWER-transmission electron microscopy -uses ultra-thin sections of specimens -light passes through specimen, then an electromagnetic lens, to a screen or film -enables visualization of structures at the molecular level -specimen must be very thin (20-60nm) and be stained with heavy-metal salts