Pinocytosis:a
is engulfment of large particles by the cell.
b. occurs in protozoans and algae but not in more complex organisms.
c. involves the specific binding of molecules to receptors on the cell surface.
d. is the nonspecific uptake of fluids by pinching inward of the plasma membrane.
e. is movement of molecules against the concentration gradient through a permeable
membrane.
D
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Even if detected early, PKU cannot be treated to prevent the development of intellectual disability
a. True b. False Indicate whether the statement is true or false
As the trees in England become less sooty due to
pollution controls on factories, which of the following should occur? a. Fewer dark moths should survive. b. Numbers of dark and light moths won’t change due to stabilizing selection. c. Genetic mutations will be reversed. d. More light-gray moths should survive. e. Fewer dark moths should survive, and more light-gray moths should survive.
Which organ system is utilizing positive feedback within an organism?
a. the reproductive system b. the excretory system c. the endocrine system d. the lymphatic system
A research lab is trying to produce new antibiotics. They come up with drugs that detach the hydrophilic heads from the phospholipids in plasma membranes. This drug
A. would be highly toxic and completely useless for human beings-we also have plasma membranes with hydrophilic head groups!
B. would be highly toxic only to bacteria, making it an excellent drug to develop and test further. Humans have a different phospholipid structure in their cell plasma membranes than bacteria.
C. would generally not be toxic enough to damage Gram-negative bacteria, as their plasma membranes lie under a thick layer of peptidoglycan.
D. would be highly toxic for human beings, but might be useful as a topical antibiotic skin cream. The top layer of skin cells is dead anyway, so it wouldn't matter if this damaged those cells. It could NOT be taken internally, though, by human beings.