All of these answers are true of A-B exotoxins except __________.
A) tThe B portion of the toxin binds to surface receptors on host cells
B) they consist of two polypeptide components
C) many exotoxins are A-B toxins
D) the A portion of the toxin is the active component
E) they are produced only by gram-negative bacteria
Ans: E) they are produced only by gram-negative bacteria
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Flatworms have _______ nerve cords that run the length of their bodies, while nemotodes have _____.
a. one, two b. two, three c. two, four d. one, four
Which of the following statements best describes the gametes of most animals?
a. A sperm is large and motile; an egg is small and nonmotile. b. A sperm is small and nonmotile; an egg is large and motile. c. A sperm is large and nonmotile; an egg is small and motile. d. A sperm is small and motile; an egg is large and nonmotile. e. The sperm and egg are about the same size, but only the sperm is motile.
An action potential is an abrupt and transient change in the membrane potential of an excitable cell
1.True 2.False
Which of the following is not a hormone that uses the mechanism of action of peptide hormones?
a. insulin b. oxytocin c. ADH d. ecdysone e. growth hormone