BIOD 151 Module 3 Exam Answer Key (Portage learning)

BIOD 151 Module 3 Exam Answer Key (Portage learning) 1. Gram staining - ANSWER the observations that different types of bacteria react differently to various dyes. This differentiation, based on color, divided bacteria into two categories: Gram-positive or Gram-negative 2. Gram-positive - ANSWER Thick peptidoglycan layer, Gram-positive cells appear purple 3. Gram-negative - ANSWER Thin peptidoglycan layer, Gram-negative bacteria will initially retain the crystal violet dye. Gram-negative bacteria now retain a pink color. 4. Differential staining - ANSWER a generalized term used for any staining technique that separates specimens into further subgroups. This process most often utilizes at least two dyes. 5. Heat fixation - ANSWER samples are added to a glass slide and then passed through a flame until all liquid in the sample has been removed 6. Chemical fixation - ANSWER include the use of paraformaldehyde, ethanol, or methanol. Although these processes fix the sample to the slide, it also kills the microorganism. As such, characteristics related to motility (movement) are not possible. 7. Wet mount - ANSWER a basic form of sample preparation for viewing live samples. A small liquid culture (usually just a drop) containing a microorganism of interest is prepared, added to a slide, and then covered with a glass coverslip. are used to observe the motility and behavior of an organism. 8. What is a coverslip? - ANSWER coverslip is present to both protect the objective and the specimen while also holding the microorganism in place. 9. Simple staining - ANSWER uses a solution of a positively charged dye, such as methylene blue, crystal violet, safranin, or fuchsin, to bind to and stain the negatively charged membrane of the microorganism. This simple technique is often used to quickly observe the size, shape, and arrangement of cells. 10. Negative staining - ANSWER Creates "capsule effect", Acidic dyes (anionic) that are repelled by the negative surface charge of a cell. Instead of staining the microorganism, you stain everything except the microorganism. By applying the dark stain nigrosin (or India ink) to a sample, its negative charge is repelled by the negatively charged membrane, resulting in a sharp contrast between the unstained specimen and the now dark background. Cell remains colorless, but background is stained to give a contrast 11. Acid-fast staining (also known as the Ziehl-Neelsen stain) - ANSWER a differential stain used to identify bacterial stains showing a high degree of resistance to decolorization. Differential Stains: Acid-fast Stains: Mycobacterium and Nocardia 12. For cells that resist decolorization - ANSWER Primary dye: Carbolfuchsin (red) Counterstain: Methylene (Blue) Cells remain colorless but background is stained to give a contrast Tuberculosis, leprosy, lung and skin infections 13. Giemsa - ANSWER a differential stain, Combined with Wright's stain (stains blood cells), the resulting combinatorial stain can be applied to blood smears to determine the presence (or absence) of pathogenic bacteria — human (blood) cells appear purple, and bacterial cells appear as pink. This staining is most often used for the diagnosis of malaria as well as other blood parasites. 14. Gram Stain Steps - ANSWER Heat Fixation Primary Stain Mordant Decolorizing agent Counterstain 15. Types of Differential stains - ANSWER Gram, acid-fast, endospore, hematoxylin, eosin staining 16. Types of Special Stains - ANSWER Negative stains, flagellar stains, and fluorescent stains 17. Types of simple stains - ANSWER crystal violet, safranin, fuchsin, methylene blue 18. Chemistry of Staining - ANSWER stains are salts, which break down into positively and negatively charged ions 19. What senses contain specialized receptor cells via specialized somatic and visceral afferents? - ANSWER smell & equilibrium ( a&c) 20. the posterior portion of the outer fibrous layer of the eye is called the ____ - ANSWER sclera 21. what portion of the eye supplies blood supply to the outer layers of the eye? - ANSWER choroid (of the middle layer) 22. true or false: the more numerous type of photoreceptors are rods - ANSWER true 23. what is the correct order of how light passes through the eye? - ANSWER cornea, lens, vitreous fluid, retina 24. A patient had a CVA in the area indicated by the red x in the figure, below. What type of blindness is the patient most likely to incur? Explain your reasoning. - ANSWER Bilateral left visual field blindness. The right optic tract is damaged. All the sensory information from the left visual fields travels together after the optic chiasm to the right side of the brain. 25. A patient has a brain tumor in the area indicated by the red x in the figure, below. What type of blindness is the patient most likely to incur? Explain your reasoning. - ANSWER Left eye blindness because there is damage to the left optic nerve. Information from the left visual field has not yet crossed at the optic chiasm. Both peripheral and nasal fields of the left eye would be missing.