Questions and answers for exam Preparation

MCQs

Total Questions : 193 | Page 2 of 20 pages

Question 11. Which of the following enzymes plays an important role in the Cori " cycle?

Glucokinase
Glucose-6-phosphate dehydrogenase
Lactate dehydrogenase
Glucose isomerase

Discuss Question

Answer: Option C. -> Lactate dehydrogenase
Answer: (c).Lactate dehydrogenase

Question 12. Regulated metabolic pathways are

compartmentalized in eukaryotes
usually regulated at the first step
committed after the first step
all of these

Discuss Question

Answer: Option D. -> all of these
Answer: (d).all of these

Question 13. When living organisms are cooled below some critical body temperature, the metabolic reactions within their cells cease to function properly. This malfunction occurs because

their enzymes lose the proper three-dimensional shape
enzyme active sites become permanently bound to substrates
the activation energy for the reaction is raised
there is insufficient molecular motion for substrates to interact

Discuss Question

Answer: Option D. -> there is insufficient molecular motion for substrates to interact
Answer: (d).there is insufficient molecular motion for substrates to interact

Question 14. Glycogen degradation requires the enzyme namely

glycogen phosphorylase and phosphoglucomutase
glycogen phosphorylase and glycogen-debranching enzyme
glycogen synthase and phosphorylase
none of the above

Discuss Question

Answer: Option B. -> glycogen phosphorylase and glycogen-debranching enzyme
Answer: (b).glycogen phosphorylase and glycogen-debranching enzyme

Question 15. The hormones, glucagon and epinephrine, stimulate glycogen breakdown to G-6-P

only in the liver
using ATP as the phosphoryl donor
directly, by binding to glycogen phosphorylase
indirectly, by first stimulating adenylate cyclase to make cAMP

Discuss Question

Answer: Option D. -> indirectly, by first stimulating adenylate cyclase to make cAMP
Answer: (d).indirectly, by first stimulating adenylate cyclase to make cAMP

Question 16. By what factor chymotrypsin enhances the rate of peptide bond hydrolysis?

10⁷
10⁸
At least 10⁹
10⁶

Discuss Question

Answer: Option C. -> At least 10⁹
Answer: (c).At least 10⁹

Question 17. What is the general mechanism of an enzyme?

It acts by reducing the activation energy
It acts by increasing the activation energy
It acts by decreasing the pH
It acts by increasing the pH

Discuss Question

Answer: Option A. -> It acts by reducing the activation energy
Answer: (a).It acts by reducing the activation energy

Question 18. The active site of chymotrypsin consists of a catalytic triad of which of the following amino acid residues?

Serine, histidine and aspartate
Serine, histidine and glutamate
Threonine, histidine and aspartate
Methionine, histidine and aspartate

Discuss Question

Answer: Option A. -> Serine, histidine and aspartate
Answer: (a).Serine, histidine and aspartate

Question 19. The polypeptide chains in chymotrypsin are linked by ___________

Hydrogen bonds
Ionic bonds
Disulfide bond
SH-SH bond

Discuss Question

Answer: Option C. -> Disulfide bond
Answer: (c).Disulfide bond

Question 20. Which of the following statements are true about the reactions at the active center of chymotrypsin?

The aspartate residue gives an electron to histidine
The aspartate residue gives a proton to histidine
The aspartate residue keeps the histidine in the correct direction
A proton moves from the aspartate to serine to histidine in the catalytic triad of chymotrypsin

Discuss Question

Answer: Option C. -> The aspartate residue keeps the histidine in the correct direction
Answer: (c).The aspartate residue keeps the histidine in the correct direction