Engineering Questions with Answers - Multiple Choice Questions

MCQs on Aerobic Respiration – TCA Cycle

1 - Question

All enzymes of the TCA cycle reside in the mitochondrial membrane.
a) True
b) False

View Answer

Answer: b
Explanation: All enzymes of the TCA cycle other than succinate dehydrogenase reside in the matrix. It is the only enzyme that takes part in both TCA cycle and electron transport chain and it resides in the inner mitochondrial membrane.




2 - Question

Which of the following is also known as Krebs cycle?
a) Electron transport chain
b) Glycolysis
c) TCA cycle
d) DNA Replication

View Answer

Answer: c
Explanation: The TCA cycle is also known as the Krebs cycle after the name of British biochemist Hans Kreb who elucidated the pathway in 1930s.




3 - Question

. How many reactions that occur in the TCA cycle transfer electrons from a substrate to an electron accepting enzyme?
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: d
Explanation: There are four such a reaction in which electron is transferred from substrate to electron accepting enzyme. In three of these, NAD+ is reduced to NADH and in one FAD reduces to FADH2.




4 - Question

Which of the following is an important end product of disassembly of fatty acids?
a) Acetyl CoA
b) Succinate dehydrogenase
c) Pyruvate
d) DNA gyrase

View Answer

Answer: a
Explanation: The metabolites of TCA cycle are also the same compounds generated by other catabolic processes in the cell. For instance, Acetyl CoA is also an important end product of disassembly of fatty acids.




5 - Question

Polysaccharides, fats and proteins break down into metabolites of __________________
a) Glycolysis
b) TCA cycle
c) RNA repair
d) Membrane synthesis

View Answer

Answer: b
Explanation: Mitochondrion is the site for final energy-conserving steps in metabolism. The energy providing macromolecules polysaccharides, fats and proteins break down into the metabolites of TCA cycle.




6 - Question

Acetyl CoA is a _____________ carbon compound.
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: b
Explanation: Acetyl CoA is a 2 carbon compound. From oxidation of pyruvate (by the pyruvate dehydrogenase) which is a 3 carbon compound, acetyl CoA is formed with the release of one molecule of CO2 and NADH each.




7 - Question

In the TCA cycle, which of the following combines with Acetyl CoA to form a 6 carbon compound?
a) oxaloacetate
b) glucose
c) pyruvate
d) thiamine

View Answer

Answer: a
Explanation: Acetyl CoA is a 2 carbon compound that combines with oxaloacetate which is a 4 carbon compound to form a 6 carbon compound, citrate. The reaction is catalyzed by citrate synthase.




8 - Question

. The enzyme aconitase is responsible for ________________
a) polymerization
b) degradation
c) assembly
d) isomerization

View Answer

Answer: d
Explanation: In the TCA cycle, aconitase is responsible for isomerization of citrate to isocitrate. Isocitrate is further oxidized by isocitrate dehydrogenase to form alpha-ketoglutarate.




9 - Question

For each molecule of glucose, how many times does the TCA cycle proceed?
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: b
Explanation: Since each molecule of glucose gives off two pyruvate molecules through the process of glycolysis, the cycle operates twice for each molecule of glucose.

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