The phospholipids of plasma membranes contain _____
a. a hydrophobic head and a hydrophilic tail
b. two hydrophobic heads and a hydrophilic tail
c. a hydrophobic head and two hydrophobic tails
d. a hydrophilic head and two hydrophobic tails
e. a hydrophilic head and two hydrophilic tails
ANSWER: d
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In viruses, genetic information flows from ________ to ________
A) RNA / virion B) nucleic acid / protein C) capsid / virion D) DNA / protein
Which of the following is not a characteristic of bacteria?
A. Organelles termed mitochondria are the site of ATP production. B. The cell wall is made of peptidoglycan or other distinct polysaccharides. C. Ribosomes are present as the site of protein synthesis. D. DNA is free in the cytoplasm.
Once bound by antibodies, an antigen is effectively opsonized and thus rendered more
A) to the complement cascade. B) susceptible to phagocytosis. C) likely to agglutinate. D) to be recognized by natural killer cells. E) likely to block the activity of a pathogen.
Which of the following is generally accepted as the origin of living organisms?
a. Life was seeded on Earth from some distant place by meteorites and comets crashing into Earth. b. Spontaneous generation c. Life originated from an oxygen-rich atmosphere on Earth. d. Life can originate from nonliving matter. e. Prebiotic chemical evolution gave rise to progressively more complex molecules and eventually to living organisms