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. G3P → 1,3-BPG and 1,3-BPG → 3-PG
- B. 1,3-BPG → 3-PG and PEP → Pyruvate
- C. G3P → 1,3-BPG and PEP → Pyruvate
- D. 2-PG → PEP and PEP → Pyruvate
Explanation: ATP is produced at two substrate-level phosphorylation steps:1) 1,3-BPG → 3-PG (via phosphoglycerate kinase)2) PEP → Pyruvate (via…
Correct answer: 1,3-BPG → 3-PG and PEP → Pyruvate- A. Acetyl-CoA
- B. Lactic acid
- C. Ethanol
- D. CO2 + H2O
Explanation: In oxygen deficiency, pyruvate is converted to lactic acid by lactate dehydrogenase, regenerating NAD⁺ needed for glycolysis to proceed.
Correct answer: Lactic acid- A. Succinyl-CoA
- B. Citrate
- C. α-Ketoglutarate
- D. Malate
Explanation: Acetyl-CoA (2C) combines with oxaloacetate (4C) via citrate synthase to form citrate (6C), the first step of the Krebs cycle.
Correct answer: Citrate- A. Synthesis of ATP, O2 and NADH
- B. Utilization of ATP, CO2 and NADPH
- C. Electron transfer from NADPH to RuBP
- D. Carbon dioxide transfer from RuBP to glucose
Explanation: Dark reaction is also called carbon-fixing reaction. It is a light-independent process in which sugar molecules are formed from carbon…
Correct answer: Utilization of ATP, CO2 and NADPH- A. Ethanol and Carbon dioxide
- B. Lactate
- C. Pyruvate
- D. Both A and B
Explanation: The end products of anaerobic respiration depend on the specific type of anaerobic process involved.
Correct answer: Both A and B- A. PS II
- B. PS I
- C. PS I and PS II
- D. PS III
Explanation: Cyclic photophosphorylation employs the use of only photosystem I (PS1).
Correct answer: PS I- A. Chlorophyll
- B. ATP
- C. Carotenoids
- D. Glucose
Explanation: Chlorophyll, is the correct answer because they are the photosynthetic pigment that comprises the reaction centers of these clusters, or…
Correct answer: Chlorophyll- A. Alcoholic fermentation
- B. Calvin cycle
- C. Aerobic respiration
- D. Lactic Acid fermentation
Explanation: The Calvin Cycle, also known as the light-independent reactions of photosynthesis, does not directly use pyruvic acid as a substrate.
Correct answer: Calvin cycle- A. Stroma of chloroplast
- B. Guard cells of stomata
- C. Thylakoid membrane of chloroplast
- D. Cytoplasm of leaf cell
Explanation: The correct answer is the thylakoid membrane of the chloroplast. The light-dependent reactions of photosynthesis occur in these membranes…
Correct answer: Thylakoid membrane of chloroplast- A. Night
- B. Noon
- C. Dusk
- D. Dawn and Dusk
Explanation: At dawn and dusk, when light intensity is low, the rate of photosynthesis and respiration may, for a short time, equal one another.
Correct answer: Dawn and Dusk- A. That water is split
- B. Light energy is converted into chemical energy
- C. That glucose is oxidized
- D. That carbon-dioxide is fixed
- E. None of the above
Explanation: The main process that occurs in the dark reaction (also known as the Calvin Cycle) in photosynthesis is the synthesis of glucose.
Correct answer: That carbon-dioxide is fixed- A. Orange
- B. Grey
- C. Yellow
- D. Blue-Green
Explanation: In paper chromatography, xanthophylls are pigments that are often responsible for giving a yellow color.
Correct answer: Yellow- A. 2
- B. 36
- C. 18
- D. 32
Explanation: In eukaryotic cells, aerobic respiration typically results in a net gain of approximately 36 ATP molecules per molecule of glucose.
Correct answer: 36- A. Lipids
- B. ATP
- C. Proteins
- D. Carbohydrates
Explanation: The immediate source of energy for cellular respiration is adenosine triphosphate, or ATP.
Correct answer: ATP- A. Citrate
- B. Alpha-ketoglutarate
- C. Succinate
- D. Fumarate
Explanation: Coenzyme A is removed from Succinyl CoA to form succinate. The reaction releases sufficient energy which is used to combine GDP and Pi…
Correct answer: Succinate- A. Mitochondrion
- B. Chloroplast
- C. Cytoplasm
- D. Nucleus
- E. Vacuole
Explanation: Glycolysis, the first stage of cellular respiration, occurs in the cytoplasm of the cell.
Correct answer: Cytoplasm- A. Glycolysis
- B. Oxidative Phospholyration
- C. Electron Transport Chain
- D. Kreb's Cycle
- E. Calvin Cycle
Explanation: The process by which one molecule of glucose splits up into molecules of pyruvate is called glycolysis.
Correct answer: Glycolysis- A. Stroma
- B. Cytosol
- C. Thylakoid Membrane
- D. No specific location
Explanation: The Calvin Cycle, also known as the dark reactions or light-independent reactions of photosynthesis, occurs in the stroma of the…
Correct answer: Stroma- A. Phosphoglycerate
- B. Phosphoglycolate
- C. Glycerate
- D. Glycolate
Explanation: When RuBP reacts with oxygen instead of CO₂ in a process called photorespiration, RuBisCO catalyzes the formation of one molecule of…
Correct answer: Phosphoglycolate- A. 3-phosphoglycerate
- B. Glyceraldehyde 3 - phosphate
- C. 1, 3 bisphosphoglycerate
- D. Ribulose bisphosphate
Explanation: The first stable compound formed during the Calvin Cycle is 3-phosphoglycerate (3-PGA).
Correct answer: 3-phosphoglycerate