Filarial roundworms cause elephantiasis by
(a) encysting in muscle tissue.
(b) promoting the growth of fatty tumors.
(c) obstructing lymphatic vessels.
(d) laying numerous eggs in the joints of their hosts.
(c) obstructing lymphatic vessels.
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Antimicrobial susceptibility testing should be performed when
a. a single bacterial species grows from any body site. b. an isolate has a predictable susceptibility profile to therapeutic drugs of choice. c. reliable standardized methods for testing a clinically significant isolate exist. d. administering intravenous or oral antibio-tics to treat an infection.
Flowering can be regulated by light, temperature, gibberellin levels, or internal factors. What do all of these different flowering pathways have in common?
A. All four pathways result in a decrease in LEAFY (LFY) expression, which induces flowering. B. All four pathways result in an increase in CONSTANS (CO) expression, which induces flowering. C. All four pathways result in an increase in LEAFY (LFY) expression, which induces flowering. D. All four pathways result in a decrease in CONSTANS (CO) expression, which induces flowering.
Why is penicillin ineffective against gram-negative bacteria?
a. Penicillin is not toxic to gram-negative bacteria. b. Penicillin is pushed away from the cell membrane by the fimbriae. c. Gram-negative bacterial do not have receptors for penicillin to attach to. d. Gram-negative bacteria do not have channels or pores in its membrane for penicillin to pass through. e. Penicillin cannot reach the thin peptidoglycan layer easily because it is protected by the bacteria’s outer membrane.
Look at the diagram of a cross-section of a cell membrane below. The cell membrane controls movement of materials into and out of the cell. The following particles are moving from high concentration to low concentration and are using a carrier protein. How would you describe this type of movement across the membrane?
A. simple osmosis B. active transport C. simple diffusion D. facilitated diffusion