BIOD 171 MODULE 3 EXAM Questions & Answers Rated 100% Correct!!

A nanometer is defined as: - Answer-10 -9 or one-billionth of a meter True or False: A nanometer is longer than a micrometer - Answer-False A nanometer is 1000x smaller than a micrometer Resolution and contrast are two critical factors that influence your ability to see an object. Explain each. - Answer-Resolution refers to the distance between two objects at which the objects can still be seen as separate. Poor or low resolution means two or more objects may appear as one. Contrast on the other hand is the difference in light absorbance between two objects. Poor contrast gives a high background and makes the visualization of multiple objects difficult. For instance, trying to identify 2 dark colored objects at night (low light = low contrast) versus the same 2 objects in the middle of a sunny afternoon (bright light against 2 dark objects = high contrast). Assuming a fixed ocular, identify the part of the microscope you would adjust to enhance the magnification of a sample. - Answer-Objective Only the oculars (eyepiece) and the objectives contribute to the magnification of the sample. Since the eyepiece is fixed, only the objectives could be altered. Assuming a constant (non-adjustable) light source power, identify the part of the microscope you would adjust to limit the amount of light entering the microscope. - Answer-Iris diaphragm What is the total magnification on (relative to your eye) of a sample imaged with a 60x objective and a 10x eyepiece? Show your math. - Answer-60x objective x 10x ocular = 600x magnificationTrue or False: Staining is often required to image a cell that is adherent and flat (thin). - Answer-True Adherent, flat and unstained cells are almost invisible due to the limits on both resolution and contrast. Therefore, cell staining is often required to adequately image the sample. True or False: A cell that is adherent, flat (thin), and unstained is easily identified using bright field microscopy - Answer-False: Adherent, flat cells are almost invisible due to the limits on both resolution and contrast Which of the following could be seen clearly by the unaided eye? Select all that apply. A. Bacteria with diameter of 24 μm B. Protozoa with diameter of 150 μm C. Virus with a diameter of 0.2 μm D. Skin cell with diameter of 1500 μm - Answer-B. Protozoa with diameter of 150 μm D. Skin cell with diameter of 1500 μm The unaided eye can, on average, clearly resolve objects > 100 μm 2. Which of the following could NOT be seen clearly by the unaided eye? Select all that apply. A. Bacteria with diameter of 24 μm B. Protozoa with diameter of 150 μm C. Virus with a diameter of 0.2 μm D. Skin cell with diameter of 1500 μm - Answer-A. Bacteria with diameter of 24 μm C. Virus with a diameter of 0.2 μm The unaided eye can, on average, clearly resolve objects > 100 μm1. Label the following unmarked microscope components (numbered arrows) by matching it with the components provided (letters). - Answer-1F- eyepiece 2D- neck 3B- fine adjustment knob 4G- objective 5A- stage 6H- base This type of microscope is best suited for visualizing GFP, RFP, and YFP proteins. - Answer-Fluorescence This type of microscope utilizes ultraviolet (UV) light to illuminate stained objects. - Answer-Fluorescence This type of microscope uses a specialized condenser and objective to amplify the slight differences between cells and background. - Answer-Phase-contrast This type of microscope enhances contrast between specimen and background but does not permit the visualization of intracellular structures. - Answer-Dark Field This type of microscope uses neither halogen nor UV light sources but rather lasers to illuminate stained cells in high resolution. - Answer-Confocal This type of microscope is capable of capturing images in multiple focal planes, rendering a specimen in 3-D - Answer-Confocal Identify what type of electron microscope was used to capture the following image and explain your choice. (picture labeled B) - Answer-The image was captured using a Scanning Electron Microscope (SEM). The above image shows the trademark 'shell' image (no subcellular organelles are visible) reminiscent of SEM. Only TEM is capable of visualizing subcellular substrucutres.Identify what type of electron microscope was used to capture the following image and explain your choice. (picture labeled A) - Answer-The above image is captured via a Transmission Electron Microscope (TEM). Even at 20nm resolution (inset image), subcellular substructures are still visible. The image lacks the outside 'shell' only appearance of SEM. Gram-Positive cells appear [answer1] in color due to a [answer2] peptidoglycan layer in the cell wall. - Answer-1. Purple 2. Thick Gram-Negative cells appear [answer1] in color due to a [answer2] peptidoglycan layer in the cell wall. - Answer-1. Pink 2. Thin True or False: A Giemsa stain can be used to determine the presence of pathogenic bacteria. - AnswerTrue Pathogenic bacteria would appear pink while non-pathogenic bacteria would appear purple. True or False: The distinguishing characteristic of Gram-Negative bacteria is the presence of LPS in the outer membrane. - Answer-True