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Multiple Choice Quiz
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1
A competitive antagonist
A)blocks the endogenous signaling molecule from binding and causes that cell to respond
B)blocks the endogenous signaling molecule from binding but does not trigger a response by the cell
C)can be a drug that minics the normal action of the endogenous messenger molecule
D)B and C
E)A and C
2
Receptor down regulation
A)Refers to an increase in the total number of receptors for that messenger on the target cell
B)Reduces the target cell’s responsiveness to frequent or intense stimulation by the receptor agonist
C)Desensitizes the target cell
D)A and C
E)B and C
3
Receptor activation
A)is usually the initial step leading to a cell’s ultimate response to the messenger
B)is always the initial step leading to the cell’s ultimate response to the messenger
C)refers to increased cleavage of ATP by the receptor
D)is directly due to alterations in cell proteins
E)B and D
4
First messengers are substances that enter or are generated in the cytoplasm as a result of receptor activation.
A)True
B)False
5
Protein kinases
A)serve as a switch to convert a receptor into an ion channel in the plasma membrane
B)are any enzyme that phosphorylates other proteins by transferring a phosphate group from ATP
C)can phosphorylate enzymes
D)A and C
E)B and C
6
Calcium can act as a second messenger because
A)Increased cytosolic calcium levels can activate kinases
B)electrical stimuli acting via voltage-gated Ca channels can increase calcium entry into cells
C)chemical stimuli through receptor interaction can increase calcium release from intracellular storage sites
D)A and B
E)A, B and C
7
Eicosanoids
A)are released from endoplasmic reticulum
B)are synthesized from arachidonic acid in plasma membrane
C)are synthesized from arachidonic acid in the cytoplasm
D)include prostaglandins
E)B and D
8
Receptors can only be deactivated when the concentration of the first messenger molecules in the region of the receptor decreases.
A)True
B)False
9
Which of the following statements about G proteins is not correct:
A)G proteins are involved in the signaling by lipid-soluble hormones
B)G proteins can either stimulate or inhibit adenylyl cyclase
C)G proteins are involved in the signaling of a large class of receptors that have a similar general structure involving 7 membrane-spanning domains
D)G proteins can couple a receptor to the opening of an ion channel
E)A-D are all correct
10
Which of the following statements is not true regarding intracellular signaling mediated by activation of phospholipase C:
A)Phospholipase C can be activated by a G protein coupled receptor
B)Phospholipase C, via generation of diacyl glycerol (DAG) can activate protein kinase C
C)Phospholipase C, via generation of inositol triphosphate (IP3) and the release of intracellular calcium can activate protein kinase C
D)Phospholipase C, via generation of inositol triphosphate (IP3) and the release of intracellular calcium can activate calcium-calmodulin dependent protein kinases
E)Each of these statements is correct





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