Biochemistry Questions and Answers – Examples Of Enzymatic actions

This set of Biochemistry Multiple Choice Questions & Answers (MCQs) focuses on “Examples Of Enzymatic actions”.

1. By what factor chymotrypsin enhances the rate of peptide bond hydrolysis?
a) 107
b) 108
c) At least 109
d) 106
View Answer

Answer: c
Explanation: Chymotrypsin enhances the rate of peptide bond hydrolysis by a factor of at least 109.

2. The active site of chymotrypsin consists of a catalytic triad of which of the following amino acid residues?
a) Serine, histidine and aspartate
b) Serine, histidine and glutamate
c) Threonine, histidine and aspartate
d) Methionine, histidine and aspartate
View Answer

Answer: a
Explanation: Aspartate holds the histidine side chain in the correct direction to accept proton from serine.

3. Which of the following statements are true about the reactions at the active center of chymotrypsin?
a) The aspartate residue gives an electron to histidine
b) The aspartate residue gives a proton to histidine
c) The aspartate residue keeps the histidine in the correct direction
d) A proton moves from the aspartate to serine to histidine in the catalytic triad of chymotrypsin
View Answer

Answer: c
Explanation: Aspartate residue accepts a proton from serine.
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4. The polypeptide chains in chymotrypsin are linked by ___________
a) Hydrogen bonds
b) Ionic bonds
c) Disulfide bond
d) SH-SH bond
View Answer

Answer: c
Explanation: The protein consists of three polypeptide chains linked by disulfide bonds.

5. Which of the following is false about chymotrypsin?
a) Hydrolytic cleavage of a peptide bond by chymotrypsin has two phases
b) It is activated in the presence of trypsin
c) It is synthesized in the thyroid gland
d) Polypeptide chains in chymotrypsin are linked by S-S bonds
View Answer

Answer: c
Explanation: Chymotrypsin is synthesized in the pancreas.
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6. Which of the following is true about the structure of hexokinase?
a) U-shaped
b) T-shaped
c) E-shaped
d) G-shaped
View Answer

Answer: a
Explanation: Hexokinase has a U-shaped structure.

7. Which of the following is true?
a) Xylose is stereo chemically similar to glucose but one carbon shorter
b) Xylose binds to hexokinase in a position where it can be phosphorylated
c) Addition of xylose increases the rate of ATP hydrolysis
d) The binding of xylose is sufficient to induce a change in hexokinase to its active conformation
View Answer

Answer: b
Explanation: Xylose binds to hexokinase at a position where it cannot be phosphorylated.
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8. Which of the following catalyzes the reversible degradation of 2-phosphoglycerate to phosphoenolpyruvate?
a) Chymotrypsin
b) Hexokinase
c) Enolase
d) Trypsin
View Answer

Answer: c
Explanation: Enolase catalyzes the reversible degradation of 2-phosphoglycerate to phosphoenolpyruvate.

9. Which of the following catalyzes the reversible reaction of β-D-Glucose to glucose 6-phosphate?
a) Chymotrypsin
b) Hexokinase
c) Enolase
d) Trypsin
View Answer

Answer: b
Explanation: Hexokinase catalyzes the reversible reaction of β-D-Glucose to glucose 6-phosphate.
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10. Which of the following is false about lysozyme?
a) It is an antibacterial agent found in tears and egg white
b) The substrate of lysozyme is peptidoglycan
c) Lysozyme cleaves (β1 → 4) glycosidic C-O bonds between two types of sugar residue in the molecule NAM and NAG
d) It is a bisubstrate enzyme
View Answer

Answer: d
Explanation: Hexokinase is the bisubstrate enzyme.

Sanfoundry Global Education & Learning Series – Biochemistry.

To practice all areas of Biochemistry, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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