Biology

Cellular Respiration and Enzymes

1,721 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

The citric acid cycle is ____ step in carbohydrate metabolism.

  1. First

  2. second

  3. third

  4. fourth
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The citric acid cycle (Krebs cycle) is the third major step in carbohydrate metabolism, following glycolysis (first) and pyruvate oxidation (second). It precedes the electron transport chain (fourth).

Multiple choice

Which of the following is a biological uncoupler of oxidative phosphorylation?

  1. Thermogenin

  2. 2, 4-Dintrophenol

  3. 2, 4-Dichlorophenoxyacetic acid

  4. Ethylenediaminetetraacetic acid
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Thermogenin (UCP1) is a biological uncoupling protein that dissipates proton gradient across mitochondrial inner membrane, generating heat instead of ATP. 2,4-Dinitrophenol is a chemical uncoupler but not listed. The other options have different functions.

Multiple choice

Which of the following membrane-bound complexes in mitochondria is not a proton pump?

  1. NADH dehydrogenase

  2. Succinate dehydrogenase

  3. Cytochrome bc1

  4. Cytochrome c oxidase
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Complex II (Succinate dehydrogenase) is the only ETC complex that does not pump protons. It oxidizes succinate to fumarate and passes electrons directly to ubiquinone (CoQ) without contributing to the proton gradient. Complexes I, III, and IV all pump protons.

Multiple choice

_________ is called the energy currency of cell.

  1. ADP

  2. NADH2

  3. AMP

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

It contains high energy bonds and liberates high amount of energy on hydrolysis. It produces 7.5 kcal of energy when one phosphate group is broken and gets converted into ADP.

Multiple choice

What information does an infinitive R.Q. give about the respiration process?

  1. The substrate is a protein.

  2. The substrate is green fleshy leaves.

  3. The respiration is anaerobic.

  4. The substrate is any organic acid.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The ratio of the volume of carbon dioxide released to the volume of oxygen consumed by a body tissue or an organism in a given period is known as the respiratory quotient. The R.Q, in the absence of O2 during anaerobic respiration, is always infinitive. Hence, it is the correct answer.