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.
Last updated
Read the Bioenergetics notesFree MDCAT chapter notes with key terms1,378 questions · page 9 of 69
- A. Hexose phosphate
- B. NADP
- C. Pentose phosphate
- D. Triose phosphate
Explanation: In glycolysis (respiration), triose phosphate (glyceraldehyde3-phosphate, G3P) is formed during the breakdown of glucose.
Correct answer: Triose phosphate- A. Glycolysis
- B. Pyruvic acid oxidation
- C. Krebs cycle
- D. Respiratory chain
Explanation: The respiratory chain, or electron transport chain (ETC), is located in the inner mitochondrial membrane.
Correct answer: Respiratory chain163. Which one of the following molecules of the respiratory chain is found at the lowest energy level?
- A. Cytochrome a
- B. Cytochrome b
- C. Cytochrome a3
- D. Oxygen
Explanation: Cytochrome a3 , part of cytochrome c oxidase (Complex IV), is the final electron acceptor in the electron transport chain, and it…
Correct answer: Oxygen- A. Cytochrome b, c, a, a3
- B. Cytochrome c, b, a3, a
- C. Cytochrome a3, b, c, a
- D. Cytochrome a, a3, b, c
Explanation: The electron transport chain involves the transfer of electrons through a specific sequence of cytochromes: b, c, a, and a .
Correct answer: Cytochrome b, c, a, a3- A. Glycerol
- B. Lactic acid
- C. Pyruvate
- D. Succinic acid
Explanation: Glycolysis is the process where glucose is broken down into two molecules of pyruvate, which are three-carbon compounds.
Correct answer: Pyruvate- A. Pyruvic acid
- B. Lactic acid
- C. Ethyl alcohol
- D. Acetyl CoA
Explanation: C3H6O3 is the chemical formula for lactic acid, which is a product of anaerobic respiration in muscles.
Correct answer: Lactic acid- A. Alcohol
- B. Lactic acid
- C. Citric acid
- D. Fumaric acid
Explanation: Muscle cells carry out lactic acid fermentation. Lactic acid fermentation is a type of anaerobic respiration, which means that it does not…
Correct answer: Lactic acid- A. Fructose + H2O
- B. Glucose + CO2
- C. Alcohol + CO2
- D. H2O + CO2
Explanation: The incomplete breakdown of sugars during anaerobic respiration, especially in yeast, results in the formation of ethanol (alcohol) and…
Correct answer: Alcohol + CO2- A. Citrate
- B. Acetyl-CoA
- C. NADH
- D. Adenosine triphosphate (ATP)
Explanation: ATP is a major cellular energy carrier and acts as a feedback inhibitor of phosphofructokinase, reducing glycolysis when energy levels are…
Correct answer: Citrate- A. Glycolysis
- B. Krebs cycle
- C. Lactic acid fermentation
- D. Dark reactions
Explanation: During lactic acid fermentation, NADH is oxidized back to NAD⁺, which allows glycolysis to continue in the absence of oxygen.
Correct answer: Lactic acid fermentation- A. Lactate
- B. Pyruvate
- C. Acetaldehyde
- D. Alcohol
Explanation: In the absence of oxygen, yeast carries out alcoholic fermentation. Glucose is first converted to pyruvate, then to acetaldehyde, and…
Correct answer: Alcohol- A. 2-phosphoglycerate → PEP
- B. 3-phosphoglycerate → 2-phosphoglycerate
- C. 1,3-bisphosphoglycerate → 3-phosphoglycerate
- D. G3P → 1,3-bisphosphoglycerate
Explanation: During glycolysis, the conversion of 2-phosphoglycerate (2- PG) to phosphoenolpyruvate (PEP) is catalyzed by the enzyme enolase, where a…
Correct answer: 2-phosphoglycerate → PEP- A. 2
- B. 4
- C. 6
- D. 8
Explanation: In glycolysis, a total of 4 ATP molecules are produced in the energy payoff phase.
Correct answer: 4- A. NADH
- B. FADH2
- C. Malate
- D. ATP
Explanation: During the Krebs cycle, succinate is oxidized to fumarate, producing FADH2 as an electron carrier in the process.
Correct answer: FADH2- A. Amino acid aspartate
- B. Fumarate dehydrogenase
- C. Succinate dehydrogenase
- D. FAD+ oxidase
Explanation: Succinate dehydrogenase is the enzyme that catalyzes the conversion of succinate to fumarate in the Krebs cycle, making it the correct…
Correct answer: Succinate dehydrogenase- A. 2
- B. 12
- C. 6
- D. 3
Explanation: Starting from pyruvate (end product of glycolysis), three decarboxylation reactions occur: one during pyruvate oxidation and two during…
Correct answer: 3- A. Oxygen
- B. Cytochrome a₃
- C. NADH
- D. FADH₂
Explanation: During the respiratory chain of cellular respiration, cytochrome c oxidizes cytochrome a₃.
Correct answer: Cytochrome a₃- A. Synthesize NADP+
- B. Synthesize ADP
- C. Create electron gradient
- D. Create proton gradient
Explanation: The electron transport chain in mitochondria creates a proton gradient across the inner mitochondrial membrane.
Correct answer: Create proton gradient- A. Erythrocytes
- B. Neuron
- C. Oxyntic cell
- D. Cardiac muscle cell
Explanation: Oxidative phosphorylation takes place in mitochondria. Erythrocytes (red blood cells) lack mitochondria, so they cannot perform oxidative…
Correct answer: Erythrocytes- A. Glycolysis
- B. Oxidation of pyruvate
- C. Krebs cycle
- D. Chemiosmosis
Explanation: Chemiosmosis uses the proton gradient created by the electron transport chain to produce the majority of ATP in cellular respiration.
Correct answer: Chemiosmosis