Ch. 16

Question 1

1. Signaling by the steroid hormone estrogen is an example of _______ signaling.
   a. autocrine
   b. endocrine
   c. paracrine
   d. direct cell-to-cell

Answer 1

endocrine

Question 2

2. Signaling by neurotransmitters is an example of _______ signaling.
   a. autocrine
   b. endocrine
   c. paracrine
   d. direct cell-to-cell

Answer 2

paracrine

Question 3

3. Stimulation of T lymphocytes, leading to their synthesis of a growth factor resulting in T lymphocyte proliferation, is an example of _______ signaling.
   a. autocrine
   b. endocrine
   c. paracrine
   d. direct cell-to-cell

Answer 3

autocrine

Question 4

4. Signaling by cadherins is an example of _______ signaling.
   a. autocrine
   b. endocrine
   c. paracrine
   d. direct cell-to-cell

Answer 4

direct cell-to-cell

Question 5

6. Steroid hormones usually act via receptors that
   a. are coupled to G proteins that activate adenylyl cyclase.
   b. activate tyrosine kinases.
   c. bind to DNA.
   d. activate phospholipase C.

Answer 5

bind to DNA.

Question 6

7. Which of the following signal molecules binds to nuclear receptors?
   a. Thyroid hormone
   b. Vitamin D3
   c. Retinoic acid
   d. Estrogen

Answer 6

Thyroid hormone, Vitamin D3, and Estrogen

Question 7

8. A glucocorticoid binding to its receptor stimulates
   a. phosphorylation of a transcription factor protein that activates a gene.
   b. formation of a receptor dimer that triggers an intracellular signal pathway.
   c. formation of a receptor dimer that binds to and activates a gene.
   d. binding of the receptor monomer to a gene.

Answer 7

formation of a receptor dimer that binds to and activates a gene.

Question 8

13. Neurotransmitters act by binding to receptors that are
    a. ligand-gated ion channels.
    b. located in the cytoplasm.
    c. tyrosine-kinase receptors.
    d. not coupled to G proteins.

Answer 8

ligand-gated ion channels.

Question 9

14. Which of the following stimulates fibroblasts to proliferate and thus heal a wound?
    a. EGF
    b. NGF
    a. NO
    d. PDGF

Answer 9

PDGF

Question 10

16. Aspirin inhibits _______ synthesis.
    a. abscisic acid
    b. vasopressin
    c. estrogen
    d. prostaglandin

Answer 10

prostaglandin

Question 11

17. All eicosanoids are synthesized from
    a. cholesterol.
    b. arachidonic acid.
    c. prostaglandin.
    d. thromboxane A.

Answer 11

arachidonic acid.

Question 12

18. In plants, cytokinins stimulate
    a. cell division.
    b. cell elongation.
    c. cell enlargement.
    d. fruit ripening.

Answer 12

cell division

Question 13

19. In plant cells, auxin binds to a
    a. cell surface receptor and triggers the ras/raf pathway.
    b. nuclear receptor that changes its shape so that it can bind to and activate genes.
    c. receptor ubiquitin ligase that stimulates the degradation of transcriptional repressors, resulting in activation of genes.
    d. cell surface molecule that stimulates fluid uptake.

Answer 13

receptor ubiquitin ligase that stimulates the degradation of transcriptional repressors, resulting in activation of genes.

Question 14

20. The G protein that activates adenylyl cyclase is a
    a. monomeric G protein in the Ras family that binds GTP.
    b. dimeric G protein that separates into  and  subunits.
    c. trimeric G protein that separates into α and βγ subunits
    d. heterotrimeric G protein that separates into  and subunits

Answer 14

trimeric G protein that separates into α and βγ subunits

Question 15

21. The GTP on the G protein that is linked to adenylyl cyclase is split to GDP and Pi
    a. in the inactive state.
    b. in the process of subunit separation.
    c. upon activation by the receptor.
    d. by the active subunit.

Answer 15

in the inactive state.

Question 16

22. In an active state of a G protein,
    a. the  subunit binds to a target protein and the  subunit remains bound to the receptor.
    b. the α and βγ subunits both can bind to target proteins.
    c. the  and  subunits both can bind to target proteins.
    d. the  subunit can bind to a target protein and the  subunit remains bound to the receptor.

Answer 16

the α and βγ subunits both can bind to target proteins

Question 17

23. Cholera toxin inhibits the ability of the α subunit of Gs to split GTP. The resulting effect is the _______ of adenylyl cyclase
    a. stimulation
    b. inhibition
    c. molecular degradation
    d. increased synthesis

Answer 17

. stimulation

Question 18

26. The major function of cAMP in animal cells is to activate
    a. adenylyl cyclase.
    b. protein kinase A.
    c. protein kinase C.
    d. tyrosine kinases.

Answer 18

protein kinase A

Question 19

27. Protein kinase A is activated by
    a. phosphorylation of its catalytic subunit.
    b. phosphorylation of its regulatory subunits.
    c. binding of cAMP to its catalytic subunits.
    d. binding of cAMP to its regulatory subunits.

Answer 19

binding of cAMP to its regulatory subunits.

Question 20

28. Which of the following is not considered a second messenger?
    a. cAMP
    b. IP3
    c. Calcium
    d. Ecdysone

Answer 20

Ecdysone

Question 21

29. Protein kinase A regulates glycogen metabolism by phosphorylating glycogen synthase and
    a. phosphorylase kinase.
    b. glycogen phosphatase.
    c. glycogen phosphorylase.
    d. glucokinase.

Answer 21

. phosphorylase kinase

Question 22

30. Protein kinase A regulates glycogen metabolism by _______ glycogen synthase and _______ glycogen phosphorylase.
    a. activating; activating
    b. inactivating; inactivating
    c. activating; inactivating
    d. inactivating; activating

Answer 22

inactivating; activating

Question 23

31. CREB is activated by
    a. cAMP binding in the nucleus.
    b. phosphorylation by protein kinase A in the nucleus.
    c. cAMP binding in the cytoplasm.
    d. phosphorylation by protein kinase A in the cytoplasm.

Answer 23

phosphorylation by protein kinase A in the nucleus.

Question 24

32. Which of the following correctly describes how protein kinase A can activate genes?
    a. Nuclear protein kinase A is activated by cAMP to phosphorylate general transcription factors.
    b. Cytosolic protein kinase A is activated by cAMP to release the catalytic subunits, which move into the nucleus and phosphorylate CREB.
    c. Cytosolic protein kinase A is activated by cAMP to release the catalytic subunits, which move into the nucleus and phosphorylate general transcription factors.
    d. Nuclear protein kinase A is activated by cAMP to phosphorylate CREB.

Answer 24

Cytosolic protein kinase A is activated by cAMP to release the catalytic subunits, which move into the nucleus and phosphorylate CREB.

Question 25

33. The response initiated by protein kinase A is terminated by a. inactivation of the initial receptor. b. inactivation of the stimulatory G protein. c. degradation of cAMP. d. dephosphorylation of phosphoproteins by protein phosphatase 1.

Answer 25

dephosphorylation of phosphoproteins by protein phosphatase 1.

Question 26

34. Rhodopsin in the vertebrate retinal photoreceptor cells results in a change in the second messenger _______, leading to the opening of ion channels in the plasma membrane and the production of a nerve impulse. a. Ca2+ b. cAMP c. cGMP d. IP3

Answer 26

cGMP

Question 27

35. Most growth factor receptors are a. G protein-linked. b. protein-tyrosine kinases. c. serine-threonine protein kinases. d. intracellular receptors.

Answer 27

protein-tyrosine kinases.

Question 28

36. The first step in growth factor pathway activation is a. receptor dimerization. b. receptor phosphorylation. c. Ras activation. d. the binding of SH2-containing proteins.

Answer 28

receptor dimerization.

Question 29

37. MAP kinase is an abbreviation for _______ protein kinase. a. microtubule-associated b. mitogen-activated c. mitosis-activating d. mitosis-associated

Answer 29

mitogen-activated

Question 30

38. MEK is a protein kinase that phosphorylates _______ residues. a. threonine and tyrosine b. tyrosine c. histidine d. arginine and lysine

Answer 30

threonine and tyrosine

Question 31

39. Mutated oncogenic Ras proteins usually a. cleave GTP more rapidly than normal. b. fail to bind Raf. c. cleave GTP less rapidly than normal. d. bind GAP more tightly than normal.

Answer 31

cleave GTP less rapidly than normal

Question 32

40. Ras is a membrane-bound _______ when activated. a. small monomeric G protein that binds GTP b. dimeric G protein that separates into  and  subunits c. heterotrimeric G protein that separates into and  subunits d. trimeric G protein that separates into α and βγ subunits

Answer 32

trimeric G protein that separates into α and βγ subunits

Question 33

41. MAP kinase signal cascades are often organized into functional groups or cassettes by a. scaffold proteins. b. binding of SH2 domains to each other. c. lipid rafts. d. binding MAP kinase-responsive genes.

Answer 33

scaffold proteins.

Question 34

42. Hydrolysis of PIP2 by phospholipase C is stimulated by a. G protein-linked receptors. b. protein-tyrosine kinase receptors. c. serine-threonine kinase receptors. d. both G protein-linked receptors and protein-tyrosine kinase receptors.

Answer 34

both G protein-linked receptors and protein-tyrosine kinase receptors.

Question 35

44. Diacylglycerol and calcium activate a. protein kinase A. b. protein kinase C. c. PI 3-kinase. d. Ca2+/calmodulin-dependent kinase.

Answer 35

protein kinase C.

Question 36

45. Calcium stimulates many cellular enzymes by binding to a calcium-binding protein called a. calcineurin. b. calcinectin. c. calmodulin. d. calbindin.

Answer 36

calmodulin

Question 37

46. TGF-β receptors act by phosphorylating the protein a. Smad. b. STAT. c. ERK. d. Wnt.

Answer 37

Smad

Question 38

43. The IP3 produced by phospholipase C acts to a. open calcium channels in the plasma membrane. b. open calcium channels in the endoplasmic reticulum. c. activate IP3-dependent kinases. d. activate protein kinase C.

Answer 38

open calcium channels in the endoplasmic reticulum.