CELL BIO TEST #2
11. Short-range cell-cell communication via secreted local mediators that act on adjacent cells: A.Autocrine communication B.Paracrine communication C.Endocrine communication D.Paracellular communication
B
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10. Compact protein module thatbinds to a particular structural motif in another protein (or lipid) molecule,with which the signaling protein interacts: A.Interaction domain B.Serine/threonine domain C.Tyrosine domain D.Scaffold domain
A
13. Small molecule that is formed in the cytosol, or released into it, in response to an extracellular signal and that helps to relay the signal in the interior of the cell: A.Second messenger B.First messenger C.Tyrosine kinase D.Serine/threonine kinase
A
15. Molecule from outside the cell that communicates the behavior or actions of other cells and elicits a biological response: A.Extracellular signal molecule B.Receptor C.Adaptor D.Relay protein
A
14. Specialized cells secreting a hormone into the blood: A.Cancer cells B.Endocrine cells C.Paracrine cells D.Adjacent cells
B
16. Enzyme that transfers the terminal phosphate group of ATP to a specific amino acid of a target protein: A.Phosphatase B.Kinase C.Cyclase D.GTPase
B
22. You are interested in how cyclic-AMP-dependent protein kinase A (PKA) functions to affect learning and memory. It is known that in the neurons you are studying, PKA works via a signal transduction pathway like the one depicted in the figure. Furthermore, it is also known that activated PKA phosphorylates the transcriptional regulator called Nerd that then activates transcription of the gene Brainy. Which situation described below will lead to an increase in Brainytranscription? (PIC) A. Amutation in the Nerdgene that produces a protein that cannot be phosphorylated by PKA B. Amutation in the nuclear import sequence of PKA preventing binding to importin C. Amutation that inactivates cAMP phosphodiesterase D. Amutation that renders adenylyl cyclase unable to interact with the α subunit of the G protein
A
23. Cholera toxin ADP-ribosylates the α subunit of stimulatory G protein (Gs), blocking GTP hydrolysis. What is the effect of this toxin on intracellular cAMP? A. Cholera toxin increases cAMP by increasing activation of adenylate cyclase by the alpha subunit of Gs B. Cholera toxin decreases cAMP by preventing activation of adenylate cyclase C. Cholera toxin increases cAMP by increasing activation of adenylate cyclase by the beta-gamma (βγ) subunit of Gs D. Cholera toxin increases cAMP by increasing activation of a cAMP phosphodiesterase
A
3. Which of the following statements about molecular switches is false? A. Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off. B. Protein kinases transfer the terminal phosphate from ATP onto a protein. C. Serine/threonine kinases are the most common types of protein kinase. D. A GTP-binding protein exchanges its bound GDP for GTP to become activated.
A
34. Enzyme that participates in the desensitization of GPCRs by phosphorylating them after they have been activated by ligand binding: A.GPCR kinase (GRK) B.Protein kinase C (PKC) C.Ca2+/calmodulin-dependent kinase (CaM-kinase) D.Protein kinase A (PKA)
A
39. Ca2+-dependent protein kinase that is activated by diacylglycerol: A.Protein kinase C (PKC) B.Phospholipase C-B C.Cyclic-GMP phosphodiesterase D.CaM-kinase
A
4. Enzyme that hydrolyzes cyclic AMP to adenosine 5'-monophosphate(5'-AMP): A.Adenylyl cyclase B.Cyclic AMP-dependent protein kinase (PKA) C.Cyclic AMP phosphodiesterase D.Cyclic AMP hydrolase
A
9. Imagine that there is a kinase cascade with two sequential kinases, PK1 and PK2. Cells with either of the two kinases inactivated, do not respond to the ligand. Cells with a mutant PK1 that is permanently active, respond even in absence of the ligand. Cells with a mutant permanently active PK1 and inactive mutant PK2 respond in absence of the ligand. In the normal cascade, does PK1 activate PK2 or does PK2 activate PK1? A.PK2 activates PK1 B.PK1 activates PK2 C.Insufficient data to decide D.PK1 and PK2 activate each other
A
17. Small signal molecule secreted by the presynaptic nerve cell at a chemical synapse to relay the signal to the postsynaptic cell: A.Second messenger B.Neurotransmitter C.GTP-binding protein D.Calcium
B
2. Why is phosphorylation/dephosphorylation a prominent switch mechanism (compared to allosteric binding) A. It is a slow mechanism, that allows precision signaling B. It is a rapid mechanism to switch on/off, and universal (targeting Tyr, Ser, Thr residues) C. It is unique for each protein conformation D. None of the above
B
27. Adenylyl cyclase is activated by a G protein. Which of the following second messengers will be generated? A. ATP B. cAMP C. IP3 D. DAG
B
28. Alteration in sensitivity following repeated stimulation, reducing a cell's response to that level of stimulus. A.Sensitization B.Desensitization C.Contact-dependent signaling D.Paracrine signaling
B
32. Ubiquitous calcium-binding protein whose interaction with other proteins are modulated by changes in the intracellular concentration of Ca2+. A.Gq B.Calmodulin C.IP3 receptor D.GPCR kinase
B
36. Enzyme bound to the cytoplasmic surface of the plasma membrane that converts membrane PI(4,5)P2 to diacylglycerol and IP3: A.Cyclic-AMP-dependent protein kinase (PKA) B.Phospholipase C-β C.Cyclic AMP phosphodiesterase D.GPCR kinase
B
38. Enzyme that phosphorylates target proteins in response to a rise in intracellular cyclic AMP: A.Cyclic AMP phosphodiesterase B.Cyclic-AMP-dependent protein kinase (PKA) C.Stimulatory G protein (Gs) D.Protein kinase C (PKC)
B
40. Light-sensitive GPCR in rod photoreceptor cells of the retina: A.Ryanodine receptor B.Rhodopsin C.Golfprotein D.Stimulatory G protein (Gs)
B
41. Protein kinase,whose activity is regulated by the binding of Ca2+-activated calmodulin and which indirectly mediates the effects of Ca2+by phosphorylation of other proteins: A.Calmodulin B.Ca2+/calmodulin-dependent kinase (CaM-kinase) C.Cyclic-AMP-dependent protein kinase (PKA) D.Protein kinase C (PKC)
B
42. How do you suppose the activity of a trimeric G protein would change by a mutation that causes its reduced affinity to GDP and no change in its GTP affinity? A.The activity will decrease B.The activity will increase C.The activity will not change D.Such protein will not be functional.
B
43. Epinephrine (adrenaline) is a hormone that signals via cAMP as the second messenger: adrenaline binds to the adrenergic receptors, activates G proteins, and initiates the breakdown of glycogen in liver, muscle, and adipose cells. How would the glycogen breakdown change, if the cells were injected with non-hydrolyzable analog of GTP (it cannot be converted into GDP) in the presence of adrenaline? A, Glycogen breakdown will not be affected B. Glycogen breakdown will be increased C. Glycogen breakdown will be decreased D. None of the above
B
6. Protein that organizes several interacting intracellular signaling proteins into signaling complexes: A.Local mediator B.Scaffold protein C.Neurotransmitter D.Receptor
B
8. Kinases are key players in signal transduction with the following characteristics: A. Kinases phosphorylate protein substrates, which always causes activation of their biological functions B. Kinases use ATP to phosphorylate proteins at Ser, Thr, and Tyr sites C. Every single Ser and Thr residuein a protein can be equally phosphorylated by PKC,aslong as these residues are exposed on the protein's surface. D. Kinases normally have regulatory and catalytic domains, where the regulatory domain binds to the substrate and the catalytic domain binds to ATP.
B
1. Which amino acids are known to be phosphorylated by protein kinases? A. tyrosine, threonine, glycine B. threonine, serine, tryptophan C. serine, threonine, tyrosine D. phenylalanine, serine, tyrosine
C
12. A signal relay chain involving multiple protein kinases, each of which is activated by phosphorylation and then phosphorylates the next protein kinase in the sequence: A.Synaptic signaling B.Adaptation cascade C.Kinase cascade D.Contact-dependent signaling
C
18. Insulin acts on receptors located throughout the body. This type of signaling is an example of: A. Autocrine signaling B. Cell contact signaling C. Endocrine signaling D. Nerve mode signaling
C
24. In muscle cells, angiotensin II (a hormone) binds to its GPCR, and Gq is activated.Which of the following will most likely happen? A. IP3will cause the release of Ca2+ from plasma membrane ligated ion channels B. Protein Kinase A cleaves phosphoinositides to form DAG and IP3C. Protein kinase C will be activated by increased diacylglycerol D. Decreased Ca2+release from endoplasmic reticulum stores leads to muscle relaxation.
C
26. Which of the following events normally activates big/trimericand small G-proteins? A. GTP hydrolysis by their intrinsic GTPase activity B. Activation of an upstream GAP C. Activation of an upstream GEF D. Activation of an upstream GDI
C
31. Protein composed of three subunits, one of which is activated by the binding of GTP A.Cyclic AMPase B.Cyclic GTPase C.Trimeric GTP-binding protein D.Stimulatory G protein (Gs)
C
35. Ca2+-release channel in the ER membrane that is activated by Ca2+ binding in the absence of IP3: A.Calmodulin B.Rhodopsin C.Ryanodine receptor D.G-protein-coupled receptor (GPCR)
C
37. Second messenger that is released from a phospholipid in the plasma membrane and diffuses to the ER, where it opens Ca2+-release channels: A.Cyclic AMP B.Diacylglycerol C.Inositol 1,4,5-trisphosphate (IP3) D.Calmodulin
C
44. A few minutes after stimulating a seven-transmembrane receptor withits ligand, which would of the following would have the highest concentration? A.Receptor-ligand B.Gα-GTP C.cAMP ]D.Phosphodiesterase
C
45. If a G-protein coupled receptor, usually induced by a hormone, is degraded along with its ligand after internalization, what is the effect on the cell's ability to respond to the hormone? A. The response is enhanced. B. The cell has increased sensitivity to subsequent stimuli. C. The cell has decreased sensitivity to subsequent stimuli. D. The cell exhibits no change in responsiveness to subsequent stimuli.
C
46. Cholera toxin modifies (through ADP-ribosylation) the αsubunit of stimulatory G protein (Gs) to block GTP hydrolysis, whereas pertussis toxin modifies the α subunit of inhibitory G protein (Gi) to prevents interaction with the receptor. What is the effect of these toxins on the concentration of intracellular cAMP? A. Cholera toxin tends to increase cAMP concentration, whereas pertussis toxin tends to decrease cAMP concentration. B. Cholera toxin tends to decrease cAMP concentration, whereas pertussis toxin tends to increase cAMP concentration. C. They both tend to increase cAMP concentration. D. They both tend to decrease cAMP concentration.
C
5. Protein that binds to a GTP-binding protein and inactivates it by stimulating its GTPase activity so that the bound GTP is hydrolyzed to GDP: A.GTP-binding protein B.Guanine nucleotide exchange factor (GEF) C.GTPase activating protein (GAP) D.Monomeric GTPase
C
19. General term for a protein that binds a specific extracellular molecule (ligand) and initiates a response in the cell: A.Kinase B.Phosphatase C.Hormone D.Receptor
D
20. Protein that binds a GTP-binding protein and activates it by stimulating the release of GDP, thereby allowing the binding of GTP: A.Local mediator B.Second messenger C.Monomeric GTPase D.Guanine nucleotide exchange factor (GEF)
D
21. Trimeric and small G-proteins share some common features; however, theyare different in some molecular details. Which of the following is correct? A. All G-proteins are functional through cAMP. B. The signaling of small G-protein requires GEF and GAP, but this is not true for trimeric G-proteins. C. The βγ subunits of trimeric G-protein do not have signaling function; they have only a structural role to form heterotrimeric G-protein. D. Both trimeric and small G-proteins have intrinsic GTPase activity. In trimeric G-proteins, it is located on the Gαsubunit.
D
25. Which of the following is an immediate consequence of activation of phospholipase C-β (PLCβ)? A. Elevation of intracellular cAMP levels, leading to the activation of protein kinase A B. Elevation of PIP3levels in the plasma membrane, leading to the activation of protein kinase B C. Generation of DAG, leading to the activation of protein kinase C D. Elevation of IP3in the plasma membrane, leading to the activation of AKT.
D
29. A 6-month-old male patient presents with slight fever, rhinitis, and sneezing,as well as forceful coughs ending with the loud inspiration (whoop). Bordetella pertussiswas cultured from the nasopharynx. The toxin from this microorganism prevents the normal function of the Gαiprotein in cells of the respiratory tract. Which of the following disruptions in cell signaling take place in response to this infection? A. Calcium being unable to bind to calmodulin B. Impaired IP3-stimulated release of calcium from endoplasmic reticulum C. Increased phospholipase C activity and PIP2cleavage D. Overproduction of cAMP from uninhibited adenylyl cyclase
D
30. G protein that activates adenylyl cyclase,and thereby increases the concentration of cyclic AMP A.Ryanodine receptor B.Diacylglycerol C.Calmodulin D.Stimulatory G protein (Gs)
D
33. Cell-surface receptorthat associates with an intracellular G protein upon activation by an extracellular ligand: A.Trimeric GTP binding protein B.GPCR kinase (GRK) C.Regulator of G protein signaling (RGS) D.G-protein-coupled receptor (GPCR)
D
7. Cell-cell communication,in which the signal molecule remains bound to the signaling cells and only influences cells that physically interact with it: A.Paracrine signaling B.Synaptic signaling C.Autocrine signaling D.Contact-dependent signaling
D
48. True or false? In the regulation of molecular switches, protein kinases and guanine nucleotide exchange factors (GEFs) always turn proteins on, protein phosphatases and GTPase-activating proteins (GAPs) always turn proteins off.
False
51. True or false? There is nofundamental difference between signaling molecules that bind to the cell-surface receptors and those that bind to intracellular receptors
False
52. True or false? All second messengers are water-soluble and diffuse freely through the cytosol.
False
49. True or false? The activity of any protein regulated by phosphorylation depends upon the balance between the activities of the kinases that phosphorylate it and the phosphatases that dephosphorylate it.
True
50. True or false? Most intracellular signaling pathways provide multiple opportunities for amplifying a response to an extracellular signal.
True
