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. 1
- B. 3
- C. 4
- D. 2
Explanation: In the electron transport chain, each NADH donates electrons that ultimately reduce oxygen to water.
Correct answer: 3- A. Acetic acid
- B. Alpha-ketoglutarate
- C. Pyruvic acid
- D. Citrate
Explanation: Pyruvic acid is the primary end product of glycolysis. It must be converted into acetyl-CoA before it can enter the Krebs cycle.
Correct answer: Pyruvic acid- A. Brain
- B. Heart
- C. Liver
- D. Muscles
Explanation: During intense exercise, when oxygen level is insufficient, lactic acid fermentation occurs in skeletal muscles, leading to the…
Correct answer: Muscles- A. NADH
- B. Cytochrome a3
- C. Water
- D. Oxygen
Explanation: Oxygen is the final electron acceptor in the electron transport chain, forming water after accepting electrons.
Correct answer: Oxygen- A. Cristae
- B. Inner compartment
- C. Outer compartment
- D. Outer membrane
Explanation: The cristae are the folded structures of the inner mitochondrial membrane where oxidative phosphorylation takes place.
Correct answer: Cristae- A. ATP
- B. FMN
- C. CoA
- D. NAD
Explanation: NAD is the universal hydrogen acceptor, crucial in redox reactions. It accepts electrons and a proton to form NADH, which then…
Correct answer: NAD147. To a living organism which of the following has the greater amount of available energy per molecule?
- A. NAD
- B. ATP
- C. ADP
- D. CO2
Explanation: ATP (Adenosine Triphosphate) is the primary energy currency of the cell, storing and providing energy for a variety of cellular…
Correct answer: ATP- A. NADP
- B. Oxygen
- C. FMN
- D. ATP
Explanation: Oxygen serves as the final electron acceptor in the electron transport chain, accepting electrons from the chain and forming water.
Correct answer: Oxygen- A. Glycolysis
- B. Krebs or citric acid cycle
- C. Electron transport chain
- D. Fermentation
Explanation: The electron transport chain occurs in the inner mitochondrial membrane and directly uses oxygen.
Correct answer: Electron transport chain- A. Chloroplasts
- B. Endoplasmic reticulum
- C. Mitochondria
- D. Lysosomes
Explanation: Mitochondria are often referred to as the "powerhouse" of the cell because they are the site of oxidative phosphorylation, where the…
Correct answer: Mitochondria- A. Acetyl-CoA
- B. Hydrochloric acid
- C. Lysine
- D. PGA
Explanation: The Krebs Cycle starts with the combination of acetyl-CoA, a two-carbon compound derived from the breakdown of pyruvic acid in glycolysis…
Correct answer: Acetyl-CoA- A. Dictyosomes
- B. Mitochondrial matrix
- C. Lysosomes
- D. Vesicles of endoplasmic reticulum
Explanation: The Krebs cycle takes place in the mitochondrial matrix, which is the innermost compartment of the mitochondria.
Correct answer: Mitochondrial matrix- A. They reduce NADP
- B. They are transferred to pyruvic acid
- C. They are eliminated in the form of methane
- D. They reduce NAD+
Explanation: The hydrogen atoms and electrons removed during the oxidation of glyceraldehyde phosphate in glycolysis are used to reduce NAD to NADH.
Correct answer: They reduce NAD+- A. Glycolysis
- B. Tricarboxylic acid cycle
- C. Oxidative phosphorylation
- D. Krebs cycle
Explanation: Glycolysis occurs in the cytoplasm and breaks down one glucose molecule into two molecules of pyruvate, releasing a small amount of ATP…
Correct answer: Glycolysis155. Fermentation is
- A. Fermentation occurs in the presence of oxygen
- B. Fermentation occurs in the absence of oxygen
- C. Fermentation produces large amounts of energy
- D. Fermentation completely breaks down glucose into carbon dioxide and water
Explanation: Fermentation is a type of anaerobic respiration (without oxygen) in which glucose or other carbohydrates are broken down incompletely.
Correct answer: Fermentation occurs in the absence of oxygen- A. Ethyl alcohol
- B. Carbon dioxide
- C. Acetyl-coenzyme A
- D. Pyruvic acid
Explanation: In alcoholic fermentation during wine production, yeast forms ethyl alcohol, carbon dioxide, and pyruvic acid, but not acetyl-coenzyme A.
Correct answer: Acetyl-coenzyme A- A. (C6HI0O5)n
- B. C2H5OH
- C. C6H12O6
- D. CH3OH
Explanation: This is ethanol, which is the primary product of the fermentation of glucose by yeast.
Correct answer: C2H5OH158. When a molecule of pyruvic acid is subjected to anaerobic oxidation and forms lactic acid, there is
- A. Gain of 2 ATP molecules.
- B. Loss of 3 ATP molecules.
- C. Loss of 5 ATP molecules.
- D. Gain of 5 ATP molecules.
Explanation: In anaerobic conditions, glucose is converted to pyruvic acid through glycolysis, which produces a net gain of 2 ATP molecules.
Correct answer: Gain of 2 ATP molecules.- A. Acetylcoenzyme A
- B. ATP
- C. Pyruvate
- D. Reduced NAD
Explanation: ATP is crucial for glycolysis as it provides the initial energy required to phosphorylate glucose, allowing the process to proceed.
Correct answer: ATP- A. In the fluid matrix of cytoplasm.
- B. In the mitochondrial matrix
- C. In the nuclear sap
- D. On the cristae of a mitochondrion
Explanation: Enzymes involved in glycolysis are located in the cytoplasmic matrix, where they catalyze the sequential steps of glucose breakdown.
Correct answer: In the fluid matrix of cytoplasm.