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?
c) At least 109
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
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
Explanation: Aspartate residue accepts a proton from serine.
4. The polypeptide chains in chymotrypsin are linked by
a) Hydrogen bonds
b) Ionic bonds
c) Disulfide bond
d) SH-SH bond
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
Explanation: Chymotrypsin is synthesized in the pancreas.
6. Which of the following is true about the structure of hexokinase?
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
Explanation: Xylose binds to hexokinase at a position where it cannot be phosphorylated.
8. Which of the following catalyzes the reversible degradation of 2-phosphoglycerate to phosphoenolpyruvate?
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?
Explanation: Hexokinase catalyzes the reversible reaction of β-D-Glucose to glucose 6-phosphate.
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
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.