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Multiple Choice Questions on
Tricarboxylic Acid or TCA Cycle
1)
The
conversion of pyruvate to acetyl CoA is catalyzed by the enzyme pyruvate
dehydrogenase. In this reaction
a) NADPH is oxidized to NADP
b) NADH is oxidized to NAD
c) NADP is reduced to NADPH
d) NAD is reduced to NADH
2)
In
TCA cycle, the reaction for the conversion of pyruvate to acetyl CoA is known
as
a) Oxidative decarboxylation
b) Oxidative phosphorylation
c) Reductive biosynthesis
d) Reductive decarboxylation
3)
Which
of the following is false regarding enzyme pyruvate dehydrogenase?
a) It is a multi-enzyme complex
b) It catalyzes the reversible
reaction (conversion of pyruvate to acetyl CoA)
c) The pyruvate dehydrogenase
complex is a mitochondrial enzyme
d) It requires thiamine, flavin and
nicotine vitamin co-enzymes
4)
Which
of the following is not the regulator of pyruvate dehydrogenase?
a) Calcium
b) Acetyl CoA
c) ATP
d) Citrate
5)
Arsenic
binds to the thiol group of lipoic acid and interferes with the activity of
enzymes that require lipoic acid as a co-factor. Which of the following enzyme
does not require lipoic acid?
a) Pyruvate dehydrogenase
b) Isocitrate dehydrogenase
c) Malate dehydrogenase
d) Branched-chain amino acid
dehydrogenase
6)
Citrate
synthase is the enzyme that catalyzes the condensation of acetyl CoA and
oxaloacetate to citrate. Which of the following is an activator of this enzyme?
a) Succinyl CoA
b) NADH
c) Fatty Acyl CoA
d) ADP
7)
Which
of the following enzyme catalyzes substrate-level phosphorylation i.e
conversion of GDP to GTP?
a) Malate dehydrogenase
b) Fumarase
c) Isocitrate dehydrogenase
d) Succinyl CoA thiokinase
8)
In
Krebs cycle, when two carbon Acetyl CoA is oxidized to CO2, the total yield of
ATP is
a) 8
b) 12
c) 14
d) 16
9)
Which
of the following is not the irreversible reaction of Kreb's cycle?
a) Isocitrate dehydrogenase
b) Alpha-ketoglutarate dehydrogenase
c) Citrate synthase
d) Malate dehydrogenase
10)
Which
of the following enzyme causes congenital lactic acidosis
a) Isocitrate dehydrogenase
b) Alpha-ketoglutarate dehydrogenase
c) Pyruvate dehydrogenase
d) Malate dehydrogenase
11)
Which
of the following enzyme of the TCA cycle catalyzes co-reduction of FAD+ to
FADH2?
a) Isocitrate dehydrogenase
b) Alpha-ketoglutarate dehydrogenase
c) Succinate Dehydrogenase
d) Malate dehydrogenase
12)
TCA
cycle is also known as the amphibolic pathway (function both in oxidative and
synthetic processes). Which of the following is a correct statement regarding
a) Alpha-ketoglutarate plays a
critical role in amino acid metabolism
b) Oxaloacetate is an intermediate
for gluconeogenesis and fatty acid synthesis
c) Succinyl CoA is involved in
ketone body metabolism
d) All of the above
13)
Which
of the following metabolic intermediate activates the TCA cycle?
a) High NADH/NAD ratio
b) High ADP/ATP ratio
c) High Oxaloacetate
d) None of the above
Multiple Choice
Answers
1-
d) NAD is reduced to NADH
2-
a) Oxidative decarboxylation
3-b)
It catalyzes the reversible reaction (conversion of pyruvate to acetyl CoA)
4-d)
Citrate
5-c)
Malate dehydrogenase
6-d)
ADP
7-d)
Succinyl CoA thiokinase
8-b)
12
9-d)
Malate dehydrogenase
10-c)
Pyruvate dehydrogenase
11-c)
Succinate Dehydrogenase
12-d)
All of the above
13-c)
High Oxaloacetate