When the effects of water-soluble hormones on their target cells are considered, the hormone itself is
A. the G protein.
B. the second messenger.
C. the first messenger.
D. the hormone-response element.
E. the phospholipase.
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Question 2) In the signal transduction pathway that results in the formation of inositol triphosphate, the G protein directly activates
A. phospholipase C.
B. protein kinase A.
C. calmodulin.
D. adenylate cyclase.
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Question 3) The word cascade can be defined as a series of small waterfalls, one leading to the next.
Describe a specific second-messenger cascade that results from the series of chemical reactions (from one to the next) initiated by a hormone binding to its receptor.
What will be an ideal response?
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Question 4) The term down-regulation refers to the process by which
A. a glandular cell decreases the amount of hormone it secretes.
B. a large amount of hormone shuts down all metabolic activity in a target cell.
C. a cell decreases the number of receptors it has for a hormone.
D. a carrier protein increases the rate of degradation for a hormone and thereby decreases its blood concentration.
E. a carrier protein decreases the rate of degradation of the protein it ferries.
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Question 5) Intracellular signaling pathways within target cells are organized such that
A. each step allows for amplification of the signal where one molecule can activate many.
B. each step involves one molecule activating or synthesizing exactly one other molecule for precise control.
C. enzymes are used up and degraded after each individual reaction they catalyze.
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Question 6) Reduced hormone concentration in the blood often causes target cells to
A. up-regulate receptors in order to increase cell sensitivity.
B. up-regulate receptors in order to decrease cell sensitivity.
C. down-regulate receptors in order to increase cell sensitivity.
D. down-regulate receptors in order to decrease cell sensitivity.
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Question 7) Within the adenylate cyclase signal transduction pathways of target cells, cAMP activates
A. the G protein.
B. adenylate cyclase.
C. protein kinase.
D. the receptor.
E. transcription of a mRNA.
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Question 8) Oxytocin results in more forceful smooth muscle contractions in the uterus by causing target cells to increase production of
A. adenylate cyclase.
B. mRNA for myosin.
C. inositol triphosphate.
D. glucose.
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Question 9) Generally, the shorter the half-life of a hormone
A. the more frequently it must be replaced.
B. the less frequently it must be replaced.
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Question 10) A G protein is
A. a type of water-soluble hormone.
B. a second messenger activated by a steroid hormone.
C. a molecule that binds a guanine nucleotide and helps transduce a signal inside a target cell.
D. a receptor for a water-soluble hormone that causes arachidonic acid to be extracted from a phospholipid.
E. an enzyme that catalyzes the conversion of ATP into cyclic AMP.