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

Which of the following is a product of oxidative phosphorylation?

  1. ATP

  2. NADH

  3. FADH2

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

ATP is the primary product of oxidative phosphorylation.

Multiple choice

What is the overall efficiency of oxidative phosphorylation in terms of ATP production?

  1. Approximately 30%

  2. Approximately 50%

  3. Approximately 70%

  4. Approximately 90%
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The overall efficiency of oxidative phosphorylation in terms of ATP production is approximately 50%.

Multiple choice

Which of the following is an example of a cofactor?

  1. NADH

  2. ATP

  3. Calcium ion

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

The heme group is an example of a cofactor, which is a non-protein molecule that is required for the activity of an enzyme.

Multiple choice

What is the term for the molecule that inhibits the activity of an enzyme?

  1. Substrate

  2. Product

  3. Cofactor

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

The term for the molecule that inhibits the activity of an enzyme is inhibitor.

Multiple choice

Glycolysis is the first stage of cellular respiration in which glucose is broken down to produce energy. What is the net gain of ATP molecules during 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

During glycolysis, one molecule of glucose is broken down into two molecules of pyruvate, yielding a net gain of 2 ATP molecules.

Multiple choice

Which enzyme catalyzes the first step of glycolysis, where glucose is phosphorylated to form glucose-6-phosphate?

  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 is the enzyme responsible for the initial phosphorylation of glucose, converting it into glucose-6-phosphate.

Multiple choice

Which intermediate molecule in glycolysis is isomerized to form fructose-6-phosphate?

  1. Glucose-6-phosphate

  2. Glucose-1-phosphate

  3. Fructose-1,6-bisphosphate

  4. 3-Phosphoglycerate
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Glucose-6-phosphate is isomerized to fructose-6-phosphate by the enzyme phosphoglucomutase.

Multiple choice

Which step in glycolysis involves the cleavage of fructose-1,6-bisphosphate into two molecules of glyceraldehyde-3-phosphate?

  1. Phosphorylation

  2. Isomerization

  3. Cleavage

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

The cleavage of fructose-1,6-bisphosphate into two molecules of glyceraldehyde-3-phosphate is catalyzed by the enzyme aldolase.

Multiple choice

What is the role of glyceraldehyde-3-phosphate dehydrogenase in glycolysis?

  1. Oxidizes glyceraldehyde-3-phosphate to form 1,3-bisphosphoglycerate

  2. Converts glyceraldehyde-3-phosphate to dihydroxyacetone phosphate

  3. Phosphorylates glyceraldehyde-3-phosphate to form 1,3-bisphosphoglycerate

  4. Reduces glyceraldehyde-3-phosphate to form glycerol-3-phosphate
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Glyceraldehyde-3-phosphate dehydrogenase catalyzes the oxidation of glyceraldehyde-3-phosphate to form 1,3-bisphosphoglycerate.

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.