BIOD 171 MODULE 3 EXAM QUESTIONS AND ANSWERS DISTICTION GUARANTEED

A nanometer is defined as: - ANSWERS10 -9 or one-billionth of a meter True or False: A nanometer is longer than a micrometer - ANSWERSFalse 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. - ANSWERSResolution 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. - ANSWERSObjective 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. - ANSWERSIris 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. - ANSWERS60x objective x 10x ocular = 600x magnification True or False: Staining is often required to image a cell that is adherent and flat (thin). - ANSWERSTrue 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 - ANSWERSFalse: 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 - ANSWERSB. 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 - ANSWERSA. 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 μm 1. Label the following unmarked microscope components (numbered arrows) by matching it with the components provided (letters). - ANSWERS1F- 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. - ANSWERSFluorescence This type of microscope utilizes ultraviolet (UV) light to illuminate stained objects. - ANSWERSFluorescence This type of microscope uses a specialized condenser and objective to amplify the slight differences between cells and background. - ANSWERSPhase-contrast This type of microscope enhances contrast between specimen and background but does not permit the visualization of intracellular structures. - ANSWERSDark Field This type of microscope uses neither halogen nor UV light sources but rather lasers to illuminate stained cells in high resolution. - ANSWERSConfocal This type of microscope is capable of capturing images in multiple focal planes, rendering a specimen in 3-D - ANSWERSConfocal Identify what type of electron microscope was used to capture the following image and explain your choice. (picture labeled B) - ANSWERSThe 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) - ANSWERSThe 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. - ANSWERS1. Purple 2. Thick Gram-Negative cells appear [answer1] in color due to a [answer2] peptidoglycan layer in the cell wall. - ANSWERS1. Pink 2. Thin True or False: A Giemsa stain can be used to determine the presence of pathogenic bacteria. - ANSWERSTrue 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. - ANSWERSTrue True or False: Following the decolorization step of the Gram stain, Gram-Negative bacteria will appear colorless. - ANSWERSTrue True or False: If you wish to study the motiity of an organism you cannot heat fix, but you can chemically fix the specimen - ANSWERSFalse Both heat and chemical fixation strategies will kill the cell, making motility observation impossible Name one substance capable of chemically fixing cells to a slide. - ANSWERSAny of the following are true: Paraformaldehyde, ethanol or methanol. You suspect a patient may have TB. Once a sample has been obtained, it is sent off to the lab for an acid-fast stain. If the patient were infected with TB, describe what you would expect to see on the stained slide. - ANSWERSI would expect to see red cells (TB+) on a blue background (TB negative). You want to observe the size and shape of a cell. What is the easiest staining technique that you could perform? Name at least one dye you would use during this process. - ANSWERSSimple stainining and crystal violet could be used. True or False: If a patient is suspected of having malaria, a Giemsa stain would be an appropriate differential test to perform. - ANSWERSTrue Giesma stains are often used in the clinical setting aid in the diagnosis of blood parasites. A human blood sample from a patient with a suspected parasite needs to be stained for diagnosis. Which stain should be selected? - ANSWERSGiemsa Select the type of microscopy used to generate the image: (black background with green glowing cells) - ANSWERSFlorescence microscopy You are the lead technician in the Microbiology Department's core Microscopy lab. You are given a list what different scientists would like to observe in their samples. You must match these samples with appropriate type of microscopy. 1. A slide stained with fuchsin simple stain to observe the size of the cells 2. The organelles in a living ciliate 3. An unstained sample that cannot be visualized with bright field because microorganism absorbs very little light 4. Theprotein trafficking of tagged proteins of interest under experimental conditions in a cell 5. Build a 3-dimensional image of a cell A. Bright field B. Phase contrast C. Dark field D. Florescence E. Confocal - ANSWERS1. A 2. B 3. C 4. D 5. E