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 enzyme catalyzes the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate?

  1. Phosphoglycerate kinase

  2. Phosphoglyceromutase

  3. Enolase

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

Phosphoglycerate kinase catalyzes the transfer of a phosphate group from 1,3-bisphosphoglycerate to ADP, forming 3-phosphoglycerate and ATP.

Multiple choice

What is the role of enolase in glycolysis?

  1. Converts 3-phosphoglycerate to 2-phosphoglycerate

  2. Converts 2-phosphoglycerate to phosphoenolpyruvate

  3. Converts phosphoenolpyruvate to pyruvate

  4. Converts dihydroxyacetone phosphate to glyceraldehyde-3-phosphate
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Enolase catalyzes the dehydration of 2-phosphoglycerate to form phosphoenolpyruvate.

Multiple choice

Which enzyme catalyzes the final step of glycolysis, where phosphoenolpyruvate is converted to pyruvate?

  1. Phosphoglycerate kinase

  2. Phosphoglyceromutase

  3. Enolase

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

Pyruvate kinase catalyzes the transfer of a phosphate group from phosphoenolpyruvate to ADP, forming pyruvate and ATP.

Multiple choice

How many molecules of NADH are produced during glycolysis?

  1. 2

  2. 4

  3. 6

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

Two molecules of NADH are produced during glycolysis, one from the oxidation of glyceraldehyde-3-phosphate and one from the oxidation of phosphoenolpyruvate.

Multiple choice

Which molecule is the final product of glycolysis?

  1. Glucose-6-phosphate

  2. Fructose-1,6-bisphosphate

  3. Glyceraldehyde-3-phosphate

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

Pyruvate is the final product of glycolysis, which is then converted to acetyl-CoA and enters the citric acid cycle.

Multiple choice

What is the overall energy yield of glycolysis in terms of ATP molecules?

  1. 2 ATP

  2. 4 ATP

  3. 6 ATP

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

Glycolysis yields a net gain of 2 ATP molecules, along with 2 molecules of NADH and 2 molecules of pyruvate.

Multiple choice

Which metabolic pathway continues after glycolysis to further break down pyruvate and generate energy?

  1. Citric acid cycle

  2. Electron transport chain

  3. Oxidative phosphorylation

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

The citric acid cycle, also known as the Krebs cycle, is the next step in cellular respiration after glycolysis, where pyruvate is further broken down to generate energy.

Multiple choice

What is the significance of glycolysis in cellular metabolism?

  1. Provides energy in the form of ATP

  2. Generates NADH and FADH2 for oxidative phosphorylation

  3. Produces pyruvate for entry into the citric acid cycle

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

Glycolysis plays a crucial role in cellular metabolism by providing energy in the form of ATP, generating NADH and FADH2 for oxidative phosphorylation, and producing pyruvate for entry into the citric acid cycle.

Multiple choice

Which stage of cellular respiration occurs in the cytoplasm?

  1. Glycolysis

  2. Krebs Cycle

  3. Electron Transport Chain

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

Glycolysis, the initial stage of cellular respiration, takes place in the cytoplasm of the cell, where glucose is broken down into pyruvate, releasing energy in the form of ATP.

Multiple choice

What is the primary function of the Krebs Cycle?

  1. Generating ATP through substrate-level phosphorylation

  2. Producing NADH and FADH2 for electron transport chain

  3. Synthesizing glucose from non-carbohydrate sources

  4. Breaking down amino acids and fatty acids
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The Krebs Cycle, also known as the Citric Acid Cycle, generates NADH and FADH2, which are high-energy electron carriers that feed into the electron transport chain for ATP production.

Multiple choice

What is the final stage of cellular respiration?

  1. Glycolysis

  2. Krebs Cycle

  3. Electron Transport Chain

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

Oxidative Phosphorylation, the final stage of cellular respiration, occurs in the mitochondrial matrix, where the energy released from the electron transport chain is used to generate ATP through the movement of protons back across the mitochondrial membrane.

Multiple choice

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

  1. Electron donors in the electron transport chain

  2. Energy carriers for ATP synthesis

  3. Substrates for glycolysis

  4. Regulators of gene expression
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

NADH and FADH2, generated in the Krebs Cycle, serve as electron donors in the electron transport chain, passing electrons along the chain to generate energy for ATP production.

Multiple choice

What is the role of ATP in cellular processes?

  1. Energy currency of the cell

  2. Building block for DNA and RNA

  3. Transport molecule for ions and molecules

  4. Signal molecule for cellular communication
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

ATP, or adenosine triphosphate, is the primary energy currency of the cell, providing energy for various cellular processes, including muscle contraction, nerve impulse transmission, and chemical synthesis.

Multiple choice

Which metabolic pathway is responsible for breaking down glucose into pyruvate?

  1. Glycolysis

  2. Krebs Cycle

  3. Electron Transport Chain

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

Glycolysis, the first stage of cellular respiration, involves the breakdown of glucose into pyruvate, releasing energy in the form of ATP and NADH.

Multiple choice

What is the net gain of ATP molecules during glycolysis?

  1. 2

  2. 4

  3. 6

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

During glycolysis, 2 molecules of ATP are produced through substrate-level phosphorylation, while 2 molecules of ATP are consumed in the preparatory phase, resulting in a net gain of 2 ATP molecules.