Biochemistry Multiple Choice Questions on “Receptor Enzymes”.
1. SH2 domain specifically binds to _____________
A. GDP
B. Ca+2
C. Phosphorylated tyrosine residues
D. Phosphorylated serine residues
Answer: C
Clarification: Phosphorylated tyrosine residues specifically binds SH2 domain during signal transduction.
2. cAMP and cGMP are derived from ____________
A. ATP and GTP by the actions of guanylate cyclase and adenylate cyclase respectively
B. ATP and GTP by the actions of adenylate cyclase and gualnlate cyclase respectively
C. GTP and ATP by the actions of adenylate cyclase and guanylate cyclase respectively
D. None of the mentioned
Answer: B
Clarification: cGMP is derived from GTP by the actions of guanylate cyclase and
cAMP is derived from ATP by the actions of adenylate cyclase respectively.
3. Which of the following is false about phosphorylation by IRS on serine residue?
A. It is an inhibitory phosphorylation
B. It is molecular mechanism for insulin resistance
C. It increases insulin levels
D. Target tissues fail to respond to circulating insulin
Answer: C
Clarification: Inhibitory serine phosphorylation is a molecular mechanism for insulin resistance which is a condition where target tissues fail to respond to circulating insulin.
4. The enzyme activated by cyclic AMP, passing on the hormonal signal is ____________
A. Protein kinase B
B. Protein kinase A
C. Protein kinase C
D. G protein receptor kinase
Answer: B
Clarification: Protein kinase A is activated by cyclic AMP, passing on the hormonal signal.
5. Protein kinase ERK is activated by phosphorylation of ____________
A. Only Thr
B. Only Tyr
C. Both Thr and Tyr
D. Only Ser
Answer: C
Clarification: Both Thr and Tyr are phosphorylated to activate the protein kinase ERK.
6. Activation of guanylyl cyclase produces ____________
A. Guanosine 3’, 5’-cyclic monophosphate
B. Guanosine 2’, 5’-cyclic monophosphate
C. Guanosine 4’, 5’-cyclic monophosphate
D. Guanosine 1’, 5’-cyclic monophosphate
Answer: A
Clarification: Guanosine 3’, 5’-cyclic monophosphate is produced by the activation of guanylyl cyclase.
7. cGMP-dependent protein kinase is also called ____________
A. Protein kinase B
B. Protein kinase A
C. Protein kinase G
D. Protein kinase C
Answer: C
Clarification: cGMP-dependent protein kinase is also called protein kinase G.
8. Which of the following is not responsible of producing diarrhea?
A. Elevation in [cGMP]
B. Increase in Cl– secretion
C. Decrease in reabsorption of water by the intestinal epithelium
D. Decrease in Cl– secretion
Answer: D
Clarification: Elevation in [cGMP] leads to increase in Cl– secretion and decrease in reabsorption of water by the intestinal epithelium.
9. Which of the following is a short-lived messenger that acts by stimulating a soluble guanylyl cyclase, raising [cGMP] and stimulating PKG?
A. NO
B. NO2
C. NO3–
D. N2O
Answer: A
Clarification: NO is a short-lived messenger that acts by stimulating a soluble guanylyl cyclase, raising [cGMP] and stimulating PKG.
10. Ras protein is a ____________
A. G-protein switch
B. Small monomeric GTPase switch protein
C. Serine-threonine kinase
D. Tyrosine kinase
Answer: B
Clarification: Ras protein is a small monomeric GTPase switch protein, involved in transmitting signals within cells.
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