Biology

Cellular Respiration and Enzymes

1,551 Questions

Explore key concepts of cellular respiration, including glycolysis, the Krebs cycle, and the electron transport chain. These questions also cover ATP production, anaerobic respiration, and essential metabolic pathways. This topic forms a core part of the biology syllabus for many competitive examinations.

Glycolysis and metabolic pathwaysKrebs cycle processesElectron transport chainATP production countAnaerobic respiration products

Cellular Respiration and Enzymes Questions

Multiple choice

Which of the following is/are examples of the amphibolic cycle?

  1. TCA cycle
  2. Calvin cycle
  3. Hatch slack cycle

  1. Only1

  2. Only 2

  3. Only 3

  4. Only 1 and 2

  5. Only 2 and 3
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The term amphibolic is used to describe a biochemical pathway that involves both catabolism and anabolism. The Tricarboxylic acid cycle (TCA cycle or Krebs Cycle) is a good example of the amphibolic pathway. The first reaction of the cycle, in which oxaloacetate (a four carbon compound) condenses with acetate (a two carbon compound) to form citrate (a six carbon compound) is typically anabolic. The next few reactions, which are intramolecular rearrangements, produce isocitrate. The following two reactions are typically catabolic. CO2 is lost in each step and succinate (a four carbon compound) is produced.

Multiple choice

In the C4 cycle, carbon dioxide is absorbed by ______________.

  1. oxaloacetic acid

  2. phosphoenol pyruvic acid

  3. malic acid

  4. ribulose biphosphate

  5. phosphoglyceraldehyde
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Phosphoenol pyruvic acid absorbs the carbon dioxide in the mesophyll cells and converts it into oxaloacetic acid in the C4 cycle.

Multiple choice

Zn2+ serves as a cofactor for

  1. arginase

  2. hexokinase

  3. carbonic anhydrase

  4. glutathione peroxidise

  5. pyruvate kinase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Zn2+ serves as a cofactor for carbonic anhydrase.

Multiple choice

Match the entries of Group - I with those in Group - II.

 
Group - I
Group - II
P. Histidine ammonia-lyase 1. Estrogen biosynthesis
Q. Adrenodoxin reductase 2. Catalyse ammonia and urocanic acid formation
R. Aromatase 3. Oxidation of uric acid
S. Urate oxidase 4. First electron transfer of mitochondrial P450

  1. P - 2, Q - 4, R - 1, S - 3

  2. P - 4, Q - 2, R - 1, S - 3

  3. P - 3, Q - 2, R - 1, S - 4

  4. P - 4, Q - 3, R - 2, S - 1

  5. P - 1, Q - 4, R - 2, S - 3
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The enzyme histidine ammonia-lyase converts histidine into ammonia and urocanic acid. Adrenodoxin reductase is a mitochondrial flavoprotein. The enzyme functions as the first electron transfer protein of mitochondrial P450 systems. Aromatase, also called estrogen synthetase, is an enzyme responsible for a key step in the biosynthesis of estrogens. The enzyme urate oxidase (UO), catalyses the oxidation of uric acid to 5-hydroxyisourate. Hence, the correct sequence of codes is P - 2, Q - 4, R - 1, S - 3.

Multiple choice

Production of glucose from the metabolism of amino acids, lactate and glycerol in the liver is known as ______.

  1. glycogenolysis

  2. gluconeogenesis

  3. glycogenesis

  4. none of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Gluconeogenesis is the metabolic pathway of producing glucose from non-carbohydrate substrates like amino acids (from protein breakdown), lactate (from anaerobic glycolysis), and glycerol (from fat breakdown). Glycogenolysis is glycogen breakdown, glycogenesis is glycogen synthesis, so the correct answer is gluconeogenesis.

Multiple choice

The pyruvic acid formed during glycolysis is oxidized to CO2 and H2O in a cycle called

  1. calvin cycle

  2. nitrogen cycle

  3. hill reaction

  4. krebs cycle
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Pyruvic acid from glycolysis enters the mitochondrial matrix and is converted to acetyl-CoA, which then enters the Krebs cycle (citric acid cycle). In this cycle, acetyl-CoA is completely oxidized to CO2 and H2O, generating NADH, FADH2, and GTP/ATP. The Calvin cycle fixes CO2 in photosynthesis, Hill reaction is part of photosynthesis, and nitrogen cycle is a biogeochemical cycle.

Multiple choice

Which of the following statements is/are false?

a. Archaebacteria derive the energy for their metabolic activities from the oxidation of chemical energy sources.

b. Methanogens manufacture methane as the result of their metabolic activities.

c. Prokaryotic cells of bacteria have an outer plasma membrane that surrounds the cell wall, which in turn surrounds cytoplasm dotted with ribosomes.

  1. Only a

  2. Both a and b

  3. Only b

  4. Both b and c

  5. Only c
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This is the correct option.

Multiple choice

The pyruvic acid transported to the mitochondrial matrix is

  1. directly used in Krebs cycle

  2. indirectly used in Krebs cycle

  3. not utilised in Krebs cycle

  4. All of the above are correct
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The pyruvic acid transported into the mitochondrial matrix is not directly used in the Krebs cycle. First it loses a molecule of CO2 as NAD+ is reduced to NADH. The remaining molecules, called acetyl group, attaches to coenzyme to form acetyl coenzyme A. The conversion of  pyruvic acid to acetyl CoA links glycolysis and the Krebs cycle. Pyruvic acid is the final product of glycolysis and acetyl CoA is the compound that enters the Krebs cycle.