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. Acetyl-CoA
- B. Oxaloacetate
- C. Lactic acid
- D. Citric acid
Explanation: Before entering the Krebs cycle, pyruvate is decarboxylated and oxidized into acetyl-CoA by the pyruvate dehydrogenase complex.
Correct answer: Acetyl-CoA- A. Phosphorylation
- B. Photophosphorylation
- C. Non-Cyclic Phosphorylation
- D. Cyclic Phosphorylation
Explanation: In cyclic photophosphorylation, electrons released from the reaction center of Photosystem I (PSI) are cycled back to the chlorophyll…
Correct answer: Cyclic Phosphorylation- A. Non-Cyclic Photophosphorylation
- B. Cyclic Photophosphorylation
- C. Both Cyclic and Non-Cyclic Photophosphorylation
- D. Oxidative Phosphorylation
Explanation: The Z-scheme is a concept in photosynthesis that describes the electron flow through the photosystems during the light-dependent…
Correct answer: Non-Cyclic Photophosphorylation- A. Cristae
- B. Matrix
- C. Outer membrane
- D. Ribosomes
Explanation: The site of oxidative phosphorylation in mitochondria is the inner mitochondrial membrane.
Correct answer: Cristae- A. Glucose
- B. Sucrose
- C. Fructose
- D. Insulin
Explanation: The most common respiratory substrate (a substance that undergoes oxidation in cellular respiration to produce energy) is glucose.
Correct answer: Glucose- A. Glycolysis
- B. Ribulose Bisphosphate
- C. Glyceraldehyde 3-phosphate
- D. NADH
Explanation: In the oxidative phase, each molecule of glyceraldehyde 3-phosphate (produced earlier in the preparatory phase) undergoes dehydrogenation.
Correct answer: Glyceraldehyde 3-phosphate- A. 1
- B. 2
- C. 3
- D. 4
Explanation: In one turn of the Krebs cycle, one molecule of ATP, one molecule of FADH2, and three molecules of NADH are produced.
Correct answer: 3428. Which one of the following is the stage of cellular respiration for which oxygen is not essential:
- A. Glycolysis
- B. Pyruvate oxidation
- C. Krebs's cycle
- D. Electron Transport Chain
Explanation: The stage of cellular respiration for which oxygen is not essential is glycolysis.
Correct answer: Glycolysis- A. Acetic acid (active)
- B. Citrate
- C. NAD
- D. FAD
Explanation: Pyruvate, the end product of glycolysis, moves from the cytosol to the mitochondrial matrix, where it undergoes oxidative decarboxylation.
Correct answer: Acetic acid (active)- A. 2 ATP
- B. 3 ATP
- C. 4 ATP
- D. 6 ATP
Explanation: Every molecule of NADH (nicotinamide adenine dinucleotide) that enters the Electron Transport Chain (ETC) during cellular respiration…
Correct answer: 3 ATP- A. Cytochrome A
- B. Oxygen
- C. Cytochrome a3
- D. Cytochrome C
Explanation: The final acceptor of electrons in the respiratory chain is oxygen (O2).
Correct answer: Oxygen- A. Pyruvic acid
- B. Ethanol
- C. Lactic acid
- D. Glucose
Explanation: The end product of anaerobic respiration in humans and other mammals is lactic acid.
Correct answer: Lactic acid- A. Respiration
- B. Photosynthesis
- C. Oxidation Reduction
- D. Photophosphorylation
Explanation: The biochemical process that occurs within a cell to break down complex compounds to produce energy is called cellular respiration.
Correct answer: Respiration- A. Phytol
- B. Porphyrin ring
- C. Pyrrole
- D. Thylakoid membrane
Explanation: The part of the chlorophyll molecule that absorbs light is the porphyrin ring, which is a complex cyclic structure containing a centrally…
Correct answer: Porphyrin ring- A. Violet Light
- B. Green Light
- C. Red Light
- D. Yellow Light
Explanation: Chlorophyll-a is the primary form of chlorophyll used in photosynthesis.
Correct answer: Violet Light- A. Pyruvate to Glucose
- B. Glucose to Pyruvate
- C. Citric acid to CO2
- D. Both Pyruvate to Glucose and Glucose to Pyruvate
Explanation: The term "glycolysis" refers to the conversion of glucose into pyruvate.
Correct answer: Glucose to Pyruvate- A. Glucose
- B. CO2
- C. Rubisco
- D. Oxaloacetate
Explanation: In the citric acid cycle (also known as the Krebs cycle or tricarboxylic acid cycle), acetyl-CoA combines with oxaloacetate to initiate…
Correct answer: Oxaloacetate- A. Chlorophyll a and b have the same absorption spectra.
- B. Chlorophyll a and b have different absorption spectra.
- C. Chlorophyll a and carotenoids have the same absorption spectra.
- D. Carotenoids and chlorophyll b have the same absorption spectra.
Explanation: Yes, chlorophyll-a and chlorophyll-b, the two main types of chlorophyll found in photosynthetic organisms, have slightly different…
Correct answer: Chlorophyll a and b have different absorption spectra.- A. Calvin Cycle
- B. Bundle Sheath Cells
- C. PEP Carboxylase
- D. CO2 Fixation in Mesophyll Cells
Explanation: In C4 plants, CO2 fixation occurs in the mesophyll cells, but it follows a unique pathway compared to C3 plants.
Correct answer: CO2 Fixation in Mesophyll Cells- A. Photosynthesis
- B. Photosystem
- C. Photosynthetic cluster arrangement
- D. Calvin system
Explanation: The organization of photosynthetic pigments into clusters is referred to as a 'photosystem.' A photosystem is a complex of pigments and…
Correct answer: Photosystem