Which of the following is true of mature T cells?
a. they mature in the bone marrow
b. they produce antibodies
c. they do not bind to antigens directly
d. antigens to which they bind must be
presented to them first by another T cell
e. more than one of these is true of mature T
cells
C
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Enzymes function primarily by
a. forcing the reactants into an altered environment which in turn creates a change in the free energy of the reactants relative to the products. b. altering the equilibrium point of a particular reaction to favor the formation of products. c. increasing the probability that the reactants will come into close proximity to each other in the proper orientation for forming the transition state molecule. d. removing reactants from solution in a set ratio that enhances the chances of the remaining individual reactants interacting with each other. e. changing the ratio of reactants to products so that the forward reaction is favored.
Which statement about taste receptors is NOT true?
A. Taste receptors are found only on the tongue in animals. B. Taste receptors generate nerve impulses in associated sensory nerve fibers. C. Taste receptors recognize sweet, sour, bitter, salty and umami sensations. D. Taste receptors are chemoreceptors. E. Taste receptors are located within taste buds in humans.
The branching "tree of life" analogy
A) accurately reflects evolution because once a split occurs, species on different branches evolve independently. B) has been discredited because it does not help us understand evolutionary relationships among organisms. C) fails to account for horizontal gene transfer, in which species on different branches exchange genes.
When energy flows from one trophic level to another, only a small amount is actually used. Which of the following uses of energy by an organism allows for the least amount of transfer to a different trophic level?
A. growth B. excretion C. cellular respiration D. death E. reproduction