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 the first stage of cellular respiration?

  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 two molecules of pyruvate.

Multiple choice

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, two molecules of ATP are produced, along with two molecules of pyruvate.

Multiple choice

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

  1. 2 ATP

  2. 4 ATP

  3. 6 ATP

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

The Krebs Cycle directly produces two molecules of ATP per molecule of glucose.

Multiple choice

Which stage of cellular respiration generates the most ATP?

  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, along with Oxidative Phosphorylation, generates the majority of ATP during cellular respiration.

Multiple choice

What is the final electron acceptor in the Electron Transport Chain?

  1. Oxygen

  2. Hydrogen

  3. Carbon Dioxide

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

Oxygen serves as the final electron acceptor in the Electron Transport Chain.

Multiple choice

What is the role of NADH and FADH2 in cellular respiration?

  1. They carry electrons from glycolysis and the Krebs Cycle to the Electron Transport Chain

  2. They produce ATP through substrate-level phosphorylation

  3. They regulate the activity of enzymes involved in cellular respiration

  4. They transport glucose into the cell
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

NADH and FADH2 are electron carriers that transfer electrons from glycolysis and the Krebs Cycle to the Electron Transport Chain.

Multiple choice

What is the overall efficiency of cellular respiration in terms of energy conversion?

  1. Approximately 20%

  2. Approximately 40%

  3. Approximately 60%

  4. Approximately 80%
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Cellular respiration has an overall efficiency of approximately 40%, meaning that about 40% of the energy stored in glucose is converted into ATP.

Multiple choice

Which of the following is NOT a product of cellular respiration?

  1. ATP

  2. Carbon Dioxide

  3. Water

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

Oxygen is a reactant, not a product, of cellular respiration.

Multiple choice

What is the name of the molecule that is produced during glycolysis and serves as the starting point for the Krebs Cycle?

  1. Pyruvate

  2. Acetyl CoA

  3. Citrate

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

Pyruvate is the molecule produced during glycolysis that is converted into Acetyl CoA, which then enters the Krebs Cycle.

Multiple choice

Which of the following enzymes is responsible for catalyzing the conversion of pyruvate to Acetyl CoA?

  1. Pyruvate Dehydrogenase

  2. Citrate Synthase

  3. Succinate Dehydrogenase

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

Pyruvate Dehydrogenase is the enzyme that catalyzes the conversion of pyruvate to Acetyl CoA.

Multiple choice

What is the name of the molecule that is produced during the Krebs Cycle and serves as the starting point for the Electron Transport Chain?

  1. Pyruvate

  2. Acetyl CoA

  3. NADH

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

NADH is the molecule produced during the Krebs Cycle that serves as the starting point for the Electron Transport Chain.

Multiple choice

Which of the following enzymes is responsible for catalyzing the conversion of NADH to NAD+ in the Electron Transport Chain?

  1. NADH Dehydrogenase

  2. Succinate Dehydrogenase

  3. Cytochrome Oxidase

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

NADH Dehydrogenase is the enzyme that catalyzes the conversion of NADH to NAD+ in the Electron Transport Chain.

Multiple choice

What is the name of the enzyme that is responsible for catalyzing the synthesis of ATP from ADP and inorganic phosphate during oxidative phosphorylation?

  1. ATP Synthase

  2. Pyruvate Dehydrogenase

  3. Citrate Synthase

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

ATP Synthase is the enzyme that catalyzes the synthesis of ATP from ADP and inorganic phosphate during oxidative phosphorylation.

Multiple choice

Which metabolic pathway is utilized by some extremophiles to generate energy in the absence of oxygen, such as in deep-sea hydrothermal vents or anoxic sediments?

  1. Glycolysis

  2. Citric Acid Cycle

  3. Electron Transport Chain

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

Fermentation is a metabolic pathway that allows organisms to generate energy in the absence of oxygen. It involves the breakdown of organic compounds, such as glucose, without the participation of an electron transport chain.

Multiple choice

Which enzyme catalyzes the conversion of orotic acid to uridine monophosphate (UMP)?

  1. Orotidine 5'-phosphate decarboxylase

  2. Uridine kinase

  3. Cytidine kinase

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

Orotidine 5'-phosphate decarboxylase catalyzes the decarboxylation of orotic acid 5'-phosphate (OMP) to form UMP, which is the first committed step in the de novo synthesis of pyrimidine nucleotides.