Lakshya Education MCQs

Question: When one molecule of glucose is completely oxidised during aerobic respiration, how many molecules of carbon dioxide are released due to tricarboxylic acid cycle?
Options:
A.One
B.Two
C.Three
D.Four
Answer: Option D
: D

Six carbon dioxide molecules are released by complete oxidation of one glucose molecules. Two carbon dioxide molecules are released during oxidative decarboxylation reaction when the glycolytic products, that is two molecules of pyruvate areconverted into two molecules of acetyl CoA and channelled into the Kreb's cycle. And four carbondioxide molecules are released during theKreb’s cycle, during the breakdown of two molecules of isocitrate to alpha-ketoglutarate and the breakdown of alpha-ketoglutarates to succinyl CoA.

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More Questions on This Topic :

Question 1. The mechanism of ATP formation both in chloroplast and mitochondria is explained by ______.
  1.    Relay pump theory of Godlewski
  2.    Munch’s pressure/mass flow model
  3.    Chemiosmotic theory of Mitchell
  4.    Cholondy – Went’s model
Answer: Option C
: C

As per Peter Mitchell’s chemiosmotic – coupling hypothesis, outward pumping of protons across the inner chloroplast or mitochondrial membrane results in accumulation of protons between outer and inner membrane. A proton gradient is thus established. As protons now flow back passively down the gradient, the proton motive force is utilized to synthesize ATP.
Question 2. When one molecule of glucose is completely oxidised during aerobic respiration, how many molecules of carbon dioxide are released due to tricarboxylic acid cycle?
  1.    One
  2.    Two
  3.    Three
  4.    Four
Answer: Option D
: D

Six carbon dioxide molecules are released by complete oxidation of one glucose molecules. Two carbon dioxide molecules are released during oxidative decarboxylation reaction when the glycolytic products, that is two molecules of pyruvate areconverted into two molecules of acetyl CoA and channelled into the Kreb's cycle. And four carbondioxide molecules are released during theKreb’s cycle, during the breakdown of two molecules of isocitrate to alpha-ketoglutarate and the breakdown of alpha-ketoglutarates to succinyl CoA.
Question 3. Which of the following molecules enters the citric acid cycle, after being broken down to acetyl CoA?
  1.    Lysine
  2.    Leucine
  3.    Fatty acids
  4.    All of the above
Answer: Option D
: D

When carbohydrates are not available, other substrates are used for respiration. Proteins are broken down to amino acids and the amino acids can be used for respiration. Some amino acids enter the oxidative phosphorylation pathway as acetyl CoA, while others form pyruvate, oxaloacetate, alpha-ketoglutarate etc. Fatty acids basically enter citric acid cycle as acetyl CoA.
Question 4. Link enzyme in cellular respiration which catalyzes the substrate produced during glycolysis, and funnels it into the Kreb's cycle is ______.
  1.    Citrate synthetase
  2.    Pyruvate dehydrogenase
  3.    Isocitrate dehydrogenase
  4.    Succinyl thiokinase
Answer: Option B
: B

Pyruvic acid synthesized in glycolysis must enter inside the mitochondria, where oxidative decarboxylation occurs in the presence of NAD+and coenzyme-A. This results in the formation of acetyl CoA which can enter the Kreb's cycle. This reaction is catalyzed by pyruvate dehydrogenase.
Question 5. In Kreb’s cycle ______.
  1.    ADP is converted to ATP
  2.    acetyl-CoA is converted to CO2 and H2O
  3.    glucose is converted in CO2
  4.    pyruvic acid is converted to ATP
Answer: Option B
: B

Kreb’s cycle, also known as tricarboxylic acid cycle is a process in whichthe glycolytic product - pyruvic acid is converted to CO2and H2O. Pyruvic acid enters Kreb's cycle as acetyl-CoA. Kreb's cycle takes place in the mitochondria.
Question 6. In Kreb’s cycle ______.
  1.    ADP is converted to ATP
  2.    acetyl-CoA is converted to CO2 and H2O
  3.    glucose is converted in CO2
  4.    pyruvic acid is converted to ATP
Answer: Option B
: B

Kreb’s cycle, also known as tricarboxylic acid cycle is a process in whichthe glycolytic product - pyruvic acid is converted to CO2and H2O. Pyruvic acid enters Kreb's cycle as acetyl-CoA. Kreb's cycle takes place in the mitochondria.

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