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

What is the final product of glycolysis?

  1. Pyruvate

  2. Acetyl-CoA

  3. Citrate

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

The final product of glycolysis is pyruvate, which is a three-carbon molecule. Pyruvate is then converted into acetyl-CoA, which enters the citric acid cycle.

Multiple choice

How many molecules of ATP are produced during the conversion of one molecule of glucose to two molecules of pyruvate?

  1. 2

  2. 4

  3. 6

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

During the conversion of one molecule of glucose to two molecules of pyruvate, two molecules of ATP are produced during glycolysis and two molecules of ATP are produced during the conversion of pyruvate to acetyl-CoA. Therefore, the total ATP yield is 4 molecules of ATP.

Multiple choice

Which of the following is NOT a substrate for glycolysis?

  1. Glucose

  2. Fructose-1,6-bisphosphate

  3. Glyceraldehyde-3-phosphate

  4. Acetyl-CoA
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Acetyl-CoA is not a substrate for glycolysis. It is a product of glycolysis and enters the citric acid cycle.

Multiple choice

What is the name of the enzyme that catalyzes the isomerization of glucose-6-phosphate to fructose-6-phosphate?

  1. Hexokinase

  2. Phosphoglucomutase

  3. Phosphofructokinase-1

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

Phosphoglucomutase catalyzes the isomerization of glucose-6-phosphate to fructose-6-phosphate. This reaction is necessary for the continuation of glycolysis.

Multiple choice

Which of the following is NOT a product of glycolysis?

  1. Pyruvate

  2. Acetyl-CoA

  3. NADH

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

Acetyl-CoA is not a product of glycolysis. It is a product of the citric acid cycle, which occurs after glycolysis.

Multiple choice

What is the name of the enzyme that 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. This reaction is also known as the Embden-Meyerhof-Parnas pathway.

Multiple choice

Which of the following is NOT a step in glycolysis?

  1. Phosphorylation of glucose

  2. Isomerization of glucose-6-phosphate

  3. Cleavage of fructose-1,6-bisphosphate

  4. Decarboxylation of pyruvate
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Decarboxylation of pyruvate is not a step in glycolysis. It is a step in the citric acid cycle, which occurs after glycolysis.

Multiple choice

What is the name of the enzyme that 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 conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate. This reaction generates one molecule of ATP for each molecule of 1,3-bisphosphoglycerate that is converted.

Multiple choice

Which of the following is NOT a fate of pyruvate after glycolysis?

  1. Conversion to acetyl-CoA

  2. Conversion to lactate

  3. Conversion to ethanol

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

Conversion to oxaloacetate is not a fate of pyruvate after glycolysis. Oxaloacetate is a product of the citric acid cycle, which occurs after glycolysis.

Multiple choice

What is the name of the enzyme that catalyzes the conversion of 3-phosphoglycerate to 2-phosphoglycerate?

  1. Phosphoglyceromutase

  2. Enolase

  3. Pyruvate kinase

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

Phosphoglyceromutase catalyzes the conversion of 3-phosphoglycerate to 2-phosphoglycerate. This reaction is necessary for the continuation of glycolysis.

Multiple choice

Which of the following is NOT a product of the conversion of one molecule of glucose to two molecules of pyruvate?

  1. 2 molecules of ATP

  2. 2 molecules of NADH

  3. 2 molecules of FADH2

  4. 2 molecules of CO2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

FADH2 is not a product of the conversion of one molecule of glucose to two molecules of pyruvate. FADH2 is a product of the citric acid cycle, which occurs after glycolysis.

Multiple choice

What is the primary function of oxidative phosphorylation in cellular respiration?

  1. To generate ATP molecules

  2. To produce NADH and FADH2

  3. To transport electrons across the mitochondrial membrane

  4. To release carbon dioxide as a waste product
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Oxidative phosphorylation is the final stage of cellular respiration, where the energy released from the oxidation of glucose is used to synthesize ATP molecules.

Multiple choice

What is the role of the electron transport chain in oxidative phosphorylation?

  1. To transfer electrons from NADH and FADH2 to oxygen

  2. To generate a proton gradient across the mitochondrial membrane

  3. To synthesize ATP molecules

  4. To produce water as a byproduct
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The electron transport chain is responsible for transferring electrons from NADH and FADH2 to oxygen, creating a proton gradient across the mitochondrial membrane.

Multiple choice

What is the function of ATP synthase in oxidative phosphorylation?

  1. To generate a proton gradient across the mitochondrial membrane

  2. To transfer electrons from NADH and FADH2 to oxygen

  3. To synthesize ATP molecules

  4. To produce water as a byproduct
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

ATP synthase uses the proton gradient generated by the electron transport chain to synthesize ATP molecules from ADP and inorganic phosphate.

Multiple choice

What is the chemiosmotic theory of oxidative phosphorylation?

  1. A theory that explains how the electron transport chain generates a proton gradient across the mitochondrial membrane

  2. A theory that explains how ATP synthase uses the proton gradient to synthesize ATP

  3. A theory that explains how oxidative phosphorylation is coupled to the synthesis of ATP

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

The chemiosmotic theory of oxidative phosphorylation explains how the electron transport chain generates a proton gradient, how ATP synthase uses the proton gradient to synthesize ATP, and how these processes are coupled to produce ATP.