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 deoxythymidine monophosphate (dTMP) to deoxythymidine (dT)?

  1. Thymidine kinase

  2. Thymidine phosphorylase

  3. Thymidine diphosphate kinase

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

Thymidine phosphorylase is the enzyme that catalyzes the conversion of dTMP to dT.

Multiple choice

What is the role of dihydrofolate reductase (DHFR) in nucleotide metabolism?

  1. To reduce dihydrofolate to tetrahydrofolate

  2. To convert folate to dihydrofolate

  3. To synthesize purine nucleotides

  4. To synthesize pyrimidine nucleotides
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

DHFR is responsible for reducing dihydrofolate to tetrahydrofolate.

Multiple choice

Which enzyme catalyzes the conversion of guanine to xanthine?

  1. Guanine deaminase

  2. Guanine kinase

  3. Guanine phosphorylase

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

Guanine deaminase is the enzyme that catalyzes the conversion of guanine to xanthine.

Multiple choice

What is the role of nicotinamide adenine dinucleotide (NAD+) in nucleotide metabolism?

  1. As an electron acceptor in redox reactions

  2. As a precursor for the synthesis of NADH

  3. As a cofactor in the synthesis of purine nucleotides

  4. As a cofactor in the synthesis of pyrimidine nucleotides
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

NAD+ is an electron acceptor in redox reactions.

Multiple choice

Which enzyme catalyzes the conversion of cytidine to uridine?

  1. Cytidine deaminase

  2. Cytidine kinase

  3. Cytidine phosphorylase

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

Cytidine deaminase is the enzyme that catalyzes the conversion of cytidine to uridine.

Multiple choice

Which of the following is the process by which cells die due to oxidative stress?

  1. Pyroptosis

  2. Ferroptosis

  3. Necroptosis

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

Ferroptosis is the process by which cells die due to oxidative stress.

Multiple choice

Which cellular process is responsible for breaking down glucose to produce energy in the form of ATP?

  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 is the first stage of cellular respiration, where glucose is broken down into pyruvate, generating a small amount of ATP and NADH.

Multiple choice

What is the role of the Krebs Cycle in cellular respiration?

  1. Glucose breakdown

  2. Pyruvate oxidation

  3. Electron transfer

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

The Krebs Cycle, also known as the Citric Acid Cycle, is a series of chemical reactions that oxidize pyruvate, derived from glycolysis, to produce NADH, FADH2, and ATP.

Multiple choice

Which molecule serves as the final electron acceptor in the Electron Transport Chain?

  1. NADH

  2. FADH2

  3. Oxygen

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

Oxygen acts as the final electron acceptor in the Electron Transport Chain, receiving electrons from NADH and FADH2 to form water.

Multiple choice

What is the primary energy currency of cells?

  1. Glucose

  2. Pyruvate

  3. ATP

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

ATP (Adenosine Triphosphate) is the primary energy currency of cells, providing energy for various cellular processes through the breakdown of its high-energy phosphate bonds.

Multiple choice

Which metabolic pathway is responsible for the breakdown of carbohydrates into smaller molecules?

  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 is the first stage of carbohydrate metabolism, where glucose is broken down into pyruvate, generating a small amount of ATP and NADH.

Multiple choice

What is the first step of glycolysis?

  1. Phosphorylation of glucose

  2. Isomerization of glucose-6-phosphate

  3. Cleavage of fructose-1,6-bisphosphate

  4. Oxidation of glyceraldehyde-3-phosphate
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The first step of glycolysis is the phosphorylation of glucose by hexokinase, which converts glucose into glucose-6-phosphate. This step requires one molecule of ATP.

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, two molecules of ATP are consumed and four molecules of ATP are produced, resulting in a net gain of two ATP molecules.

Multiple choice

Which enzyme catalyzes the cleavage of fructose-1,6-bisphosphate into two three-carbon molecules?

  1. Phosphofructokinase-1

  2. Aldolase

  3. Triose phosphate isomerase

  4. Glyceraldehyde-3-phosphate dehydrogenase
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Aldolase catalyzes the cleavage of fructose-1,6-bisphosphate into two three-carbon molecules: glyceraldehyde-3-phosphate and dihydroxyacetone phosphate.

Multiple choice

What is the role of NAD+ in glycolysis?

  1. It is reduced to NADH.

  2. It is oxidized to NAD+.

  3. It is a cofactor for enzymes.

  4. It is a substrate for enzymes.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

NAD+ is reduced to NADH during glycolysis by glyceraldehyde-3-phosphate dehydrogenase. This reaction generates one molecule of NADH for each molecule of glyceraldehyde-3-phosphate that is oxidized.