Biochemistry Problems focuses on “Fates of Pyruvate under Anaerobic Conditions: Fermentation”.
1. Which of the following is true about the enzyme producing NADH from a triose phosphate in the glycolytic pathway?
A. It produces 1, 3-biphosphoglycerate and NADH
B. It catalyzes irreversible reaction
C. It uses NAD+ and dihydroxyacetone phosphate as substrates
D. It uses FADH2 and glyceraldehyde 3-phosphate as substrates
Answer: A
Clarification: Triose phosphate, glyceraldehyde 3-phosphate is oxidized to 1, 3-biphosphoglycerate in the presence of dehydrogenase enzyme.
2. Which is the major factor(s) determining whether glucose is oxidized by aerobic or anaerobic glycolysis?
A. Ca+2
B. FADH2
C. NADH and the ATP/ADP ratio
D. Presence of high AMP
Answer: C
Clarification: NADH and the ATP/ADP ratio are the major factors determining whether glucose is oxidized by aerobic or by anaerobic glycolysis.
3. When glucose is converted to lactate by anaerobic glycolysis, equivalent number of ATPs derived is?
A. 1
B. 2
C. 3
D. 4
Answer: B
Clarification: 2 ATP molecules are released when glucose is converted to lactate by anaerobic glycolysis.
4. When one molecule of glucose is oxidized to two molecules of lactate during anaerobic glycolysis, which of the following statements is false?
A. Glyceraldehyde 3-P dehydrogenase reaction produces 2 ATP molecules
B. Lactate dehydrogenase reaction produces no ATP
C. Pyruvate kinase reaction produces 2 ATP molecules
D. Phosphofructokinase-1 reaction uses 1 ATP molecule
Answer: A
Clarification: When one molecule of glucose is oxidized to two molecules of lactate during anaerobic glycolysis, Glyceraldehyde 3-P dehydrogenase reaction does not produce 2 ATP molecules.
5. In the reduction of pyruvate to lactate, which of the following is regenerated?
A. H+
B. NADH
C. NAD+
D. Na+
Answer: C
Clarification: NAD+ is regenerated from NADH by the reduction of pyruvate to lactate.
6. For its activity, pyruvate decarboxylase requires ______________
A. Mg+2
B. Ca+2
C. Na+
D. H+
Answer: A
Clarification: Pyruvate decarboxylase requires Mg+2 in the conversion of pyruvate to acetaldehyde.
7. TPP (thiamine pyrophosphate) is derived from ____________
A. Vitamin A
B. Vitamin B1
C. Vitamin C
D. Vitamin B2
Answer: B
Clarification: TPP is a coenzyme derived from vitamin B1 (thiamine).
8. What are the end products in ethanol fermentation?
A. Ethanol and CO2
B. Ethanol and O2
C. Ethanol, H2 and CO2
D. Ethanol, O2 and CO2
Answer: A
Clarification: Overall equation of ethanol fermentation:
Glucose +2ADP + 2Pi → 2 ethanol + 2CO2 + 2ATP + 2H2O.
9. Which enzyme is involved in the pathway of ethanol fermentation?
A. Hexokinase
B. Pyruvate decarboxylase
C. Pyruvate dehydrogenase
D. Pyruvate kinase
Answer: B
Clarification: Decarboxylation of pyruvate is catalyzed by pyruvate decarboxylase.
10. Which enzyme is involved in the pathway of synthesis of acetyl-coA?
A. Hexokinase
B. Pyruvate decarboxylase
C. Pyruvate dehydrogenase
D. Pyruvate kinase
Answer: C
Clarification: In the synthesis of acetyl-coA, pyruvate dehydrogenase is involved.
of Biochemistry Problems, .