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

How many molecules of ATP are produced during glycolysis?

  1. 1

  2. 2

  3. 4

  4. 6
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Glycolysis generates a net of 2 molecules of ATP through substrate-level phosphorylation.

Multiple choice

Which enzyme is responsible for the initial phosphorylation of glucose in glycolysis?

  1. Hexokinase

  2. Phosphofructokinase

  3. Glyceraldehyde-3-phosphate dehydrogenase

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

Hexokinase catalyzes the first step of glycolysis by phosphorylating glucose to form glucose-6-phosphate.

Multiple choice

What is the role of ATP in the conversion of glucose to glucose-6-phosphate?

  1. It provides the energy for the reaction

  2. It acts as a substrate for the reaction

  3. It inhibits the reaction

  4. It has no role in the reaction
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

ATP hydrolysis provides the energy required for the phosphorylation of glucose to form glucose-6-phosphate.

Multiple choice

Which intermediate molecule in glycolysis undergoes isomerization to form fructose-6-phosphate?

  1. Glucose-6-phosphate

  2. Fructose-1,6-bisphosphate

  3. Glyceraldehyde-3-phosphate

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

Glucose-6-phosphate isomerizes to form fructose-6-phosphate, catalyzed by the enzyme phosphoglucomutase.

Multiple choice

What is the purpose of the cleavage of fructose-1,6-bisphosphate into two three-carbon molecules?

  1. To generate ATP

  2. To produce NADH and FADH2

  3. To facilitate the isomerization of glucose-6-phosphate

  4. To prepare the molecules for the next steps of glycolysis
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The cleavage of fructose-1,6-bisphosphate into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate prepares these molecules for further reactions in glycolysis.

Multiple choice

Which enzyme catalyzes the oxidation of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate?

  1. Glyceraldehyde-3-phosphate dehydrogenase

  2. Phosphoglycerate kinase

  3. Phosphoglyceromutase

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

Glyceraldehyde-3-phosphate dehydrogenase catalyzes the oxidation of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate, generating NADH in the process.

Multiple choice

What is the significance of the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate?

  1. It generates ATP

  2. It produces NADH and FADH2

  3. It prepares the molecule for the next steps of glycolysis

  4. It facilitates the isomerization of fructose-6-phosphate
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate, catalyzed by phosphoglycerate kinase, generates ATP through substrate-level phosphorylation.

Multiple choice

Which enzyme is responsible for the isomerization of 3-phosphoglycerate to 2-phosphoglycerate?

  1. Phosphoglycerate kinase

  2. Phosphoglyceromutase

  3. Enolase

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

Phosphoglyceromutase catalyzes the isomerization of 3-phosphoglycerate to 2-phosphoglycerate, preparing the molecule for the next step in glycolysis.

Multiple choice

What is the role of enolase in glycolysis?

  1. It catalyzes the isomerization of 3-phosphoglycerate to 2-phosphoglycerate

  2. It generates ATP through substrate-level phosphorylation

  3. It produces NADH and FADH2

  4. It converts 2-phosphoglycerate to phosphoenolpyruvate
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Enolase catalyzes the dehydration of 2-phosphoglycerate to form phosphoenolpyruvate, releasing a molecule of water.

Multiple choice

Which enzyme catalyzes the final step of glycolysis, converting phosphoenolpyruvate to pyruvate?

  1. Glyceraldehyde-3-phosphate dehydrogenase

  2. Phosphoglycerate kinase

  3. Phosphoglyceromutase

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

Pyruvate kinase catalyzes the final step of glycolysis, converting phosphoenolpyruvate to pyruvate, generating ATP through substrate-level phosphorylation.

Multiple choice

How many molecules of NADH are produced during glycolysis?

  1. 1

  2. 2

  3. 4

  4. 6
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Glycolysis generates a net of 2 molecules of NADH through the oxidation of glyceraldehyde-3-phosphate.

Multiple choice

What is the fate of pyruvate after glycolysis?

  1. It enters the Krebs cycle

  2. It is converted to acetyl-CoA

  3. It is used to generate ATP through oxidative phosphorylation

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

Pyruvate is converted to acetyl-CoA, which enters the Krebs cycle. It is also used to generate ATP through oxidative phosphorylation in the electron transport chain.

Multiple choice

What is the overall energy yield of glycolysis?

  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 generates a net of 2 molecules of ATP through substrate-level phosphorylation, along with 2 molecules of NADH and 2 molecules of pyruvate.

Multiple choice

What is the primary function of the Krebs Cycle?

  1. To generate ATP through oxidative phosphorylation

  2. To produce NADH and FADH2, which are used in the electron transport chain

  3. To convert pyruvate into acetyl-CoA

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

The Krebs Cycle performs multiple essential functions, including generating ATP, producing NADH and FADH2, and converting pyruvate into acetyl-CoA.

Multiple choice

How many steps are involved in the Krebs Cycle?

  1. 6

  2. 8

  3. 10

  4. 12
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The Krebs Cycle consists of a series of eight enzymatic reactions that occur in a cyclic manner.