Which of the major macromolecules—lipids, carbohydrates, proteins, and nucleic acids—contain nitrogen atoms (N)?
A. Lipids and nucleic acids
B. Carbohydrates and proteins
C. Carbohydrates and lipids
D. Nucleic acids and proteins
D. Nucleic acids and proteins
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When an enveloped virus adsorbs to the host cell with its protein spikes, the virions are taken into the cell by the process of
A. penetration. B. production. C. fusion. D. endocytosis.
Sharks and rays deal with the osmotic stress of living in seawater mainly by ____
a. active transport of ions into the body through the gills b. excreting nitrogenous wastes through their kidneys as urea
c. active transport of ions out of the body by chloride cells d. excreting excess salt through the actions of specialized salt glands in their heads e. maintaining high levels of urea and trimethylamine oxide in body fluids
The reason that approximately one-third of adults in the United States will suffer significant hearing
loss by age 65 is most likely a. frequent infections. b. inborn structural problems. c. head trauma. d. excessive noise. e. unknown causes.
The direct effect is more likely as a result of exposure to x-rays.
a. true b. false