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

What is the overall yield of ATP molecules from the complete oxidation of one molecule of glucose through cellular respiration?

  1. 2

  2. 38

  3. 32

  4. 68
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The complete oxidation of one molecule of glucose through cellular respiration yields approximately 38 molecules of ATP.

Multiple choice

Which of the following is a key regulatory enzyme in glycolysis?

  1. Hexokinase

  2. Phosphofructokinase

  3. Pyruvate kinase

  4. Lactate dehydrogenase
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Phosphofructokinase is a key regulatory enzyme in glycolysis, controlling the rate of glucose breakdown.

Multiple choice

What is the role of NADH and FADH2 in cellular respiration?

  1. Electron carriers

  2. Energy storage molecules

  3. Coenzymes

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

NADH and FADH2 are electron carriers that transfer electrons through the electron transport chain.

Multiple choice

Which of the following is a product of the Krebs Cycle that enters the electron transport chain?

  1. Pyruvate

  2. Acetyl CoA

  3. NADH

  4. FADH2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

NADH is a product of the Krebs Cycle that enters the electron transport chain, along with FADH2.

Multiple choice

What is the role of ATP synthase in cellular respiration?

  1. Generates ATP through oxidative phosphorylation

  2. Produces NADH and FADH2

  3. Converts pyruvate to acetyl CoA

  4. Regulates the Krebs Cycle
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

ATP synthase is an enzyme that generates ATP through oxidative phosphorylation, using the energy released from the flow of protons across a membrane.

Multiple choice

Which of the following is a key regulatory enzyme in the Krebs Cycle?

  1. Citrate synthase

  2. Isocitrate dehydrogenase

  3. α-Ketoglutarate dehydrogenase

  4. Malate dehydrogenase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Citrate synthase is a key regulatory enzyme in the Krebs Cycle, controlling the rate of acetyl CoA entry into the cycle.

Multiple choice

1. What is the primary function of the electron transport chain in cellular respiration?

  1. Generate ATP

  2. Produce NADH and FADH2

  3. Transport electrons from NADH and FADH2 to oxygen

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

The electron transport chain is responsible for generating ATP, producing NADH and FADH2, and transporting electrons from NADH and FADH2 to oxygen.

Multiple choice

2. How many electron carriers are involved in the electron transport chain?

  1. 2

  2. 4

  3. 6

  4. 8
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The electron transport chain consists of four electron carriers: NADH dehydrogenase, ubiquinone, cytochrome c reductase, and cytochrome c oxidase.

Multiple choice

3. Which of the following is the final electron acceptor in the electron transport chain?

  1. NADH

  2. FADH2

  3. Oxygen

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

Oxygen is the final electron acceptor in the electron transport chain, and its reduction to water is coupled to the generation of ATP.

Multiple choice

4. What is the name of the enzyme complex that catalyzes the transfer of electrons from NADH to ubiquinone?

  1. NADH dehydrogenase

  2. Ubiquinone reductase

  3. Cytochrome c reductase

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

NADH dehydrogenase is the enzyme complex that catalyzes the transfer of electrons from NADH to ubiquinone.

Multiple choice

5. Which of the following is a proton pump in the electron transport chain?

  1. NADH dehydrogenase

  2. Ubiquinone

  3. Cytochrome c reductase

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

Cytochrome c oxidase is a proton pump that pumps protons across the inner mitochondrial membrane, creating a proton gradient that drives ATP synthesis.

Multiple choice

6. What is the name of the enzyme complex that catalyzes the transfer of electrons from cytochrome c to oxygen?

  1. NADH dehydrogenase

  2. Ubiquinone reductase

  3. Cytochrome c reductase

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

Cytochrome c oxidase is the enzyme complex that catalyzes the transfer of electrons from cytochrome c to oxygen.

Multiple choice

7. How many ATP molecules are generated per NADH molecule that enters the electron transport chain?

  1. 2

  2. 3

  3. 4

  4. 5
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Three ATP molecules are generated per NADH molecule that enters the electron transport chain.

Multiple choice

8. How many ATP molecules are generated per FADH2 molecule that enters the electron transport chain?

  1. 1

  2. 2

  3. 3

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

Two ATP molecules are generated per FADH2 molecule that enters the electron transport chain.

Multiple choice

9. What is the overall efficiency of the electron transport chain in terms of ATP production?

  1. 20%

  2. 30%

  3. 40%

  4. 50%
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The overall efficiency of the electron transport chain in terms of ATP production is approximately 40%.