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. Presence of oxygen
- B. Absence of oxygen
- C. Presence or absence of oxygen
- D. High concentration of oxygen
Explanation: The correct answer is option C: presence or absence of oxygen. Glycolysis is the initial process in glucose metabolism, converting glucose…
Correct answer: Presence or absence of oxygen- A. Glucose
- B. ATP
- C. Enzymes and Coenzymes
- D. FAD
Explanation: The correct answer is option D: FAD. FAD is not involved in glycolysis; it plays a role in the citric acid cycle and the electron…
Correct answer: FAD- A. ATP to glucose
- B. G3P to ATP
- C. ATP to fructose
- D. ATP to G3P
Explanation: The correct answer is that the first step of glycolysis involves the transfer of a phosphate group from ATP to glucose, forming glucose…
Correct answer: ATP to glucose- A. Glucose
- B. Fructose 6-phosphate
- C. Glucose 6-phosphate
- D. Fructose 1, 6-biphosphate
Explanation: In the glycolytic pathway, the third step involves the phosphorylation of fructose 6-phosphate to form fructose 1,6-bisphosphate.
Correct answer: Fructose 1, 6-biphosphate- A. G3P
- B. 3PGAL
- C. Dihydroxyacetone phosphate
- D. G3P/PGAL and Dihydroxyacetone phosphate
Explanation: The fourth step of glycolysis is catalyzed by the enzyme aldolase, which cleaves fructose 1,6-bisphosphate into two three-carbon…
Correct answer: G3P/PGAL and Dihydroxyacetone phosphate- A. Oxidation of PGAL
- B. Reduction of PGAL
- C. Phosphorylation of PGAL
- D. Reduction of 3-PG
Explanation: The correct answer is the oxidation of PGAL. In glycolysis, PGAL undergoes an oxidation reaction where it donates electrons to NAD+…
Correct answer: Oxidation of PGAL- A. G3P
- B. Dihydroxyacetone phosphate
- C. 1,3-Bisphosphoglycerate
- D. Pyruvate
Explanation: Half a glucose molecule corresponds to a three-carbon unit. In glycolysis, when this unit loses two electrons as hydrogen atoms, it…
Correct answer: G3P- A. Formation of acetyl-Co-A
- B. Oxidation of acetate
- C. Reduction of NAD
- D. Decarboxylation of pyruvate
Explanation: The correct answer is the oxidation of acetate. Before the Krebs cycle starts, pyruvate undergoes decarboxylation to form acetyl-CoA, and…
Correct answer: Oxidation of acetate- A. Oxidation process is completed
- B. Decarboxylation process is completed
- C. Reduction process is completed
- D. Energy consuming process is completed
Explanation: The correct answer is that the oxidation process is completed in the Krebs cycle.
Correct answer: Oxidation process is completed- A. Formation of citrate
- B. Condensation of oxaloacetate and acetyl Co-A
- C. Coenzyme A (CoA) is released
- D. Decarboxylation and condensation of Co-A
Explanation: The correct answer is Option D: decarboxylation and condensation of acetyl-CoA.
Correct answer: Decarboxylation and condensation of Co-A- A. NAD-mediated oxidation
- B. Formation of NADH
- C. Decarboxylation
- D. Hydration
Explanation: In the formation of α-ketoglutarate during the Krebs cycle, several key changes occur that contribute to the cycle's energy yield.
Correct answer: Hydration- A. Succinate to fumarate
- B. Malate to oxaloacetate
- C. Fumarate to malate
- D. α-ketoglutarate to succinate
Explanation: In the Krebs cycle, FAD is reduced to FADH₂ during the conversion of succinate to fumarate, a reaction catalyzed by the enzyme succinate…
Correct answer: Succinate to fumarate- A. A single hydrogen atom
- B. CO2 molecule
- C. Two hydrogen atoms
- D. Water molecule
Explanation: In the Krebs cycle, succinate is converted to fumarate by the enzyme succinate dehydrogenase.
Correct answer: Two hydrogen atoms- A. 3
- B. 6
- C. 7
- D. 10
Explanation: Step number 7 of glycolysis is the correct option because it represents the second substrate-level phosphorylation in the pathway.
Correct answer: 7- A. 2 & 3
- B. 3 & 4
- C. 4 & 5
- D. 5 & 6
Explanation: In glycolysis, during step 4, the six-carbon molecule fructose 1,6-bisphosphate is split into two three-carbon molecules…
Correct answer: 4 & 5- A. 4
- B. 5
- C. 6
- D. 7
Explanation: Step number 6 is the correct option because glyceraldehyde-3-phosphate is oxidized and phosphorylated to form 1,3-bisphosphoglycerate.
Correct answer: 6- A. 6
- B. 7
- C. 9
- D. 10
Explanation: Step number 7 is the correct step because it is the first ATP-generating reaction in glycolysis.
Correct answer: 7- A. 7
- B. 8
- C. 9
- D. 10
Explanation: Step 10 of glycolysis is crucial, as it involves the conversion of phosphoenolpyruvate (PEP) into pyruvate, catalyzed by the enzyme…
Correct answer: 10- A. Coenzyme Q
- B. Molecular oxygen
- C. Cytochromes b, c, a and a3
- D. Cytochrome f
Explanation: Cytochrome f is the correct option because it is not a component of the mitochondrial respiratory chain.
Correct answer: Cytochrome f- A. NADH
- B. FADH
- C. Coenzyme Q
- D. Cytochrome C
Explanation: In the respiratory electron transport chain, the first ATP molecule is formed when electrons donated by NADH are transferred through the…
Correct answer: NADH