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 step in the Krebs Cycle involves the substrate-level phosphorylation of GDP to GTP?

  1. Conversion of succinyl CoA to succinate

  2. Conversion of isocitrate to α-ketoglutarate

  3. Conversion of malate to oxaloacetate

  4. Conversion of citrate to isocitrate
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The conversion of succinyl CoA to succinate is coupled with the substrate-level phosphorylation of GDP to GTP, generating a high-energy GTP molecule.

Multiple choice

How many molecules of NADH are produced per glucose molecule during the Krebs Cycle?

  1. 2

  2. 4

  3. 6

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

During the complete oxidation of one glucose molecule through the Krebs Cycle, a total of six molecules of NADH are produced.

Multiple choice

Which intermediate in the Krebs Cycle is directly involved in the electron transport chain?

  1. Acetyl CoA

  2. Isocitrate

  3. FADH2

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

FADH2, generated during the oxidation of succinate to fumarate, directly participates in the electron transport chain, transferring electrons to the ubiquinone pool.

Multiple choice

What is the role of oxaloacetate in the Krebs Cycle?

  1. Acceptor of acetyl CoA

  2. Electron carrier

  3. Regulator of cycle activity

  4. Final product of the cycle
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Oxaloacetate serves as the acceptor of acetyl CoA, initiating the Krebs Cycle and allowing for the continuous oxidation of acetyl groups.

Multiple choice

Which enzyme catalyzes the conversion of malate to oxaloacetate in the Krebs Cycle?

  1. Malate dehydrogenase

  2. Isocitrate dehydrogenase

  3. Succinate dehydrogenase

  4. α-Ketoglutarate dehydrogenase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Malate dehydrogenase is the enzyme responsible for the reversible conversion of malate to oxaloacetate, a crucial step in the Krebs Cycle.

Multiple choice

What is the name of the enzyme that catalyzes the decarboxylation of citrate to form α-ketoglutarate?

  1. Aconitase

  2. Isocitrate dehydrogenase

  3. α-Ketoglutarate dehydrogenase

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

Isocitrate dehydrogenase catalyzes the oxidative decarboxylation of isocitrate to form α-ketoglutarate, releasing carbon dioxide as a byproduct.

Multiple choice

Which intermediate in the Krebs Cycle is directly involved in the urea cycle?

  1. Acetyl CoA

  2. Fumarate

  3. Malate

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

Fumarate is an intermediate in the Krebs Cycle that is also involved in the urea cycle, where it is converted to argininosuccinate.

Multiple choice

What is the overall yield of ATP molecules generated per glucose molecule during the Krebs Cycle?

  1. 2

  2. 4

  3. 6

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

The Krebs Cycle directly generates two molecules of ATP per glucose molecule through substrate-level phosphorylation.

Multiple choice

Which molecule serves as the universal energy currency in cells?

  1. Glucose

  2. ATP

  3. NADH

  4. FADH2
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

ATP (adenosine triphosphate) is the universal energy currency in cells, providing energy for various cellular processes through the transfer of its terminal phosphate group.

Multiple choice

What is the first stage of cellular respiration that 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 is the initial stage of cellular respiration that takes place in the cytoplasm, where glucose is broken down into pyruvate, generating ATP and NADH.

Multiple choice

Which metabolic pathway occurs in the mitochondria and involves a series of enzymatic reactions to generate energy?

  1. Glycolysis

  2. Krebs Cycle

  3. Electron Transport Chain

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

The Krebs Cycle, also known as the Citric Acid Cycle, occurs in the mitochondria and involves a series of enzymatic reactions that break down acetyl-CoA, derived from pyruvate, to generate ATP, NADH, and FADH2.

Multiple choice

What is the final stage of cellular respiration where most ATP is produced?

  1. Glycolysis

  2. Krebs Cycle

  3. Electron Transport Chain

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

The Electron Transport Chain, located in the inner mitochondrial membrane, is the final stage of cellular respiration where electrons are transferred through a series of protein complexes, generating a proton gradient used for ATP synthesis.

Multiple choice

What is the process by which cells break down glucose to generate ATP without the use of oxygen?

  1. Cellular Respiration

  2. Glycolysis

  3. Fermentation

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

Fermentation is the process by which cells break down glucose to generate ATP without the use of oxygen, occurring in the absence of an electron transport chain.

Multiple choice

What is the primary role of the Krebs Cycle in metabolism?

  1. Energy production

  2. Glucose breakdown

  3. Electron transfer

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

The Krebs Cycle, also known as the Citric Acid Cycle, is a central metabolic pathway that generates energy in the form of ATP, NADH, and FADH2 through the breakdown of acetyl-CoA derived from various fuel molecules.

Multiple choice

Which coenzyme plays a crucial role in transferring high-energy electrons in cellular respiration?

  1. NAD+

  2. FAD

  3. CoQ

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

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme that plays a crucial role in cellular respiration by accepting electrons from various metabolic reactions and transferring them to the electron transport chain.