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. High concentration of NADH
- B. Low concentration of citrate
- C. High concentration of ATP
- D. Pyruvate decarboxylase
- E. Increase in Pyruvate
Explanation: Phosphofructokinase is inhibited by high concentrations of ATP, which signals that the cell has ample energy, reducing the need for…
Correct answer: High concentration of ATP- A. Pyruvate dehydrogenase
- B. Phosphofructokinase
- C. Glucokinase
- D. Pyruvate phosphatases
Explanation: Pyruvate dehydrogenase is responsible for converting pyruvate into acetyl-CoA.
Correct answer: Pyruvate dehydrogenase- A. Acetyl-coenzyme A
- B. Fructose
- C. ADP
- D. Pyruvic acid
Explanation: In the absence of oxygen (anaerobic conditions), pyruvic acid accepts hydrogen atoms from NADH, forming lactic acid in a process called…
Correct answer: Pyruvic acid- A. Lactic acid fermentation
- B. Alcohol fermentation
- C. Glycolysis
- D. Hydrolysis of glycogen
Explanation: In the absence of oxygen (anaerobic conditions), pyruvic acid accepts hydrogen atoms from NADH, forming lactic acid in a process called…
Correct answer: Alcohol fermentation- A. All 36 ATP molecules inside the mitochondria
- B. 2 ATP molecules during glycolysis and 34 ATP during the Krebs cycle
- C. 2 ATP molecules during glycolysis 2 in krebs cycle and 32 ATP during respiratory chain
- D. 2 ATP molecules outside the mitochondria and 34 ATP molecules inside the mitochondria
Explanation: Glycolysis produces 2 ATP in the cytoplasm, and the electron transport chain, along with chemiosmosis, generates approximately 34 ATP in…
Correct answer: 2 ATP molecules during glycolysis 2 in krebs cycle and 32 ATP during respiratory chain- A. Pyruvate
- B. Lactic acid
- C. Acetyl CoA
- D. Ethanol
Explanation: Before entering the Krebs cycle, pyruvate is converted to acetyl-CoA in a process known as pyruvate oxidation.
Correct answer: Acetyl CoA- A. ATP
- B. NADPH
- C. FAD
- D. Acetyl coA
Explanation: Acetyl CoA combines with oxaloacetate to form citrate, which marks the beginning of the Krebs cycle.
Correct answer: Acetyl coA- A. Glycolysis
- B. Pyruvic acid oxidation
- C. Krebs cycle
- D. Electron transport chain
Explanation: Glycolysis is the first stage of cellular respiration that occurs in the cytoplasm and can happen with or without oxygen.
Correct answer: Glycolysis- A. NADH and FAD
- B. NADP and FADP
- C. ATP
- D. ATP, NADH and FADH
Explanation: The Krebs cycle fully oxidizes acetyl-CoA to CO₂, producing ATP, FADH₂, and NADH.
Correct answer: ATP, NADH and FADH- A. Cytosol
- B. Membrane surface
- C. Nucleus
- D. All of these
Explanation: Glycolysis, the first stage of cellular respiration, occurs in the cytosol.
Correct answer: Cytosol- A. FAD
- B. FADH2
- C. NAD
- D. NADPH
Explanation: FAD (Flavin Adenine Dinucleotide) acts as a coenzyme in the oxidation of succinate to fumarate during the Krebs cycle.
Correct answer: FAD- A. NAD
- B. FAD
- C. Metal ion
- D. Vitamin
Explanation: Succinate dehydrogenase is an integral enzyme in the citric acid cycle and the electron transport chain.
Correct answer: FAD- A. ATP production.
- B. Sugar production.
- C. Oxygen production.
- D. Carbon dioxide production.
Explanation: The Calvin cycle uses CO₂, ATP, and NADPH to synthesize glucose (sugars) during photosynthesis.
Correct answer: Sugar production.- A. Stomata
- B. Grana
- C. Porphyrin ring
- D. Photons
Explanation: Stomata are small pores found on the surface of plant leaves and stems.
Correct answer: Stomata- A. Clusters
- B. Photosystems
- C. Stacks
- D. Both A and B are correct
Explanation: Photosynthetic pigments are organized into clusters called 'photosystems' in the thylakoid membranes.
Correct answer: Both A and B are correct- A. CO2
- B. O2
- C. H2O
- D. All of these
Explanation: During photosynthesis, plants use carbon dioxide and water to produce glucose and oxygen.
Correct answer: O2- A. Leaf.
- B. Stems
- C. Roots
- D. Branches
Explanation: The correct answer is 'Leaf'. In most plants, leaves are the primary sites for photosynthesis.
Correct answer: Leaf.- A. Animal
- B. Plants
- C. Both A and B
- D. None of these
Explanation: This option is correct as carotenoids perform protective functions in both animals and plants.
Correct answer: Both A and B- A. Glyceraldehyde-3-phosphate
- B. Dihydroxyacetone phosphate
- C. Fructose-1-phosphate
- D. Phosphofructokinase
Explanation: The missing step involves phosphorylation of fructose-6- phosphate by phosphofructokinase-1 (PFK-1), forming fructose-1,6-bisphosphate, a…
Correct answer: Phosphofructokinase- A. G6P → F6P
- B. F6P → F1,6BP
- C. G3P → 1,3-BPG
- D. 1,3-BPG → 3-PG
Explanation: ATP is consumed twice - once during Glucose → G6P (hexokinase) and once during F6P → F1,6BP (PFK-1).
Correct answer: F6P → F1,6BP