Free Bioenergetics MCQs with Answers
1,378 Bioenergetics MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Cellular respiration explains how cells release energy from glucose through glycolysis, the link reaction, Krebs cycle and electron transport chain. It includes ATP production, substrate-level and oxidative phosphorylation, aerobic versus anaerobic respiration, and the roles of mitochondria, oxygen and fermentation in energy transfer.
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- A. Pyruvic acid
- B. C2H5OH
- C. CO2
- D. Glucose
Explanation: The end product of glycolysis is pyruvic acid because glycolysis is the process of breaking down one molecule of glucose into two…
Correct answer: Pyruvic acid- A. T.C.A pathway
- B. Glycolysis
- C. Calvin pathway
- D. C4 pathway
Explanation: Glycolysis is the initial stage of cellular respiration that occurs in the cytoplasm of the cell.
Correct answer: Glycolysis- A. NADH
- B. FADH2
- C. FMNH2
- D. NADPH2
Explanation: NADH is the correct product of glycolysis because it specifically involves the reduction of NAD+ to NADH when glyceraldehyde-3-phosphate…
Correct answer: NADH- A. The end products are water and carbon dioxide
- B. Substrate-level phosphorylation takes place
- C. ATP is used
- D. ATP is formed
Explanation: The correct answer is option A: 'The end products are water and carbon dioxide.' This is incorrect because glycolysis results in the…
Correct answer: The end products are water and carbon dioxide- A. Reduced
- B. Broken into carbon fragments
- C. Oxidized
- D. Isomerized
Explanation: The conversion of pyruvic acid to acetyl-CoA is a critical step in cellular respiration.
Correct answer: Oxidized- A. Succinic acid
- B. Citric acid
- C. Malic acid
- D. Acetyl-CoA
Explanation: Acetyl-CoA is the correct option because pyruvic acid is converted into acetyl-CoA before entering the Krebs cycle.
Correct answer: Acetyl-CoA- A. 6
- B. 2
- C. 4
- D. 3
Explanation: Oxaloacetic acid has four carbon atoms, which makes it the correct option.
Correct answer: 4- A. 15 ATP
- B. 38 ATP
- C. 12 ATP
- D. 19 ATP
Explanation: Twelve ATP is the correct option because it represents the total number of ATP molecules produced from the complete oxidation of one…
Correct answer: 12 ATP- A. Succinic acid
- B. Acetyl-CoA
- C. Oxaloacetic acid
- D. Citric acid
Explanation: Acetyl-CoA is the correct option because it is the compound that forms the direct link between glycolysis and the Krebs cycle.
Correct answer: Acetyl-CoA- A. Isocitric acid → Oxalosuccinic acid → α-Ketoglutaric acid
- B. Oxalosuccinic acid → Isocitric acid → α-Ketoglutaric acid
- C. α-Ketoglutaric acid → Isocitric acid → Oxalosuccinic acid
- D. Isocitric acid → α-Ketoglutaric acid → Succinic acid
Explanation: In the Krebs cycle, the sequence of reactions involving the conversion of isocitric acid to α-ketoglutaric acid and then to succinic acid…
Correct answer: Isocitric acid → α-Ketoglutaric acid → Succinic acid931. The number of ATP molecules released in the complete oxidation of one molecule of pyruvic acid is:
- A. 2
- B. 6
- C. 15
- D. 30
Explanation: The complete oxidation of one molecule of pyruvic acid involves its conversion into acetyl-CoA during the Link reaction, which generates…
Correct answer: 15- A. Carbon dioxide
- B. Water
- C. Oxygen
- D. Cytochromes
Explanation: Cytochromes are key proteins in the electron transport chain located in the thylakoid membranes of chloroplasts during the light-dependent…
Correct answer: Cytochromes- A. Cytochromes
- B. Dehydrogenases
- C. Oxygen
- D. Hydrogen
Explanation: In aerobic respiration, oxygen functions as the final electron acceptor in the electron transport chain.
Correct answer: Oxygen- A. ATP
- B. Pyruvic acid
- C. Glucose
- D. Citric acid
Explanation: ATP is synthesised within the mitochondrion during cellular respiration, and it can leave the mitochondrion to provide energy for cellular…
Correct answer: ATP- A. Outer membrane
- B. Inner membrane
- C. Intermembrane space
- D. Matrix
Explanation: The inner membrane of the mitochondrion is where the proton gradient develops.
Correct answer: Inner membrane- A. 1
- B. 2
- C. 3
- D. 6
Explanation: Glycolysis produces two molecules of pyruvic acid from one molecule of glucose.
Correct answer: 2- A. NADPH2
- B. NADH
- C. FADH2
- D. FAD
Explanation: NADH is produced during glycolysis when glucose is oxidised, and it carries high-energy electrons to the electron transport chain.
Correct answer: NADH- A. Oxidation of pyruvic acid
- B. Electron Transport Chain
- C. Krebs cycle
- D. Glycolysis
Explanation: In aerobic respiration, the electron transport chain (ETC) is where most of the ATP is synthesised.
Correct answer: Electron Transport Chain- A. Mitochondria
- B. Golgi complex
- C. Plasma membrane
- D. Endoplasmic reticulum
Explanation: In bacteria, the respiratory enzymes are embedded in the plasma membrane.
Correct answer: Plasma membrane- A. Molecular oxygen
- B. ATP
- C. Glyceraldehyde-3-phosphate
- D. NAD+
Explanation: In glycolysis, NAD+ plays a crucial role as an electron carrier. During the oxidation of glyceraldehyde-3-phosphate to…
Correct answer: NAD+