NEET Biology: TCA cycle and electron transport system (aerobic) Practice Questions
14 free multiple-choice questions on TCA cycle and electron transport system (aerobic) (Respiration) for NEET Biology, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more NEET questions in the app →Q1. Which of the following molecules is the entry point for Acetyl-CoA into the Tricarboxylic Acid (TCA) cycle during aerobic respiration?
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Correct answer: B — Acetyl-CoA
Acetyl-CoA is the direct two-carbon molecule that combines with oxaloacetate to initiate the TCA cycle.
Q2. The overall outcome of the TCA cycle, in terms of energy yield from the carbon atoms, is the production of which molecule?
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Correct answer: A — Net production of CO₂ and H₂O
The TCA cycle completes the oxidation of the carbon fuels, leading primarily to the release of CO₂ and the generation of reduced coenzymes (NADH, FADH₂) that drive ATP synthesis.
Q3. Which molecule acts as the entry point for Acetyl-CoA into the Tricarboxylic Acid (TCA) cycle?
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Correct answer: C — Oxaloacetate
Acetyl-CoA condenses with Oxaloacetate to form Citrate, which is the first step of the TCA cycle.
Q4. Which of the following coenzymes is reduced to NADH during the oxidation of Isocitrate to α-Ketoglutarate in the TCA cycle?
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Correct answer: C — NAD⁺
The oxidation steps within the TCA cycle generate NADH by reducing NAD⁺. Specifically, Isocitrate dehydrogenase step generates NADH.
Q5. Which molecule serves as the primary entry point for Acetyl-CoA into the Tricarboxylic Acid (TCA) cycle?
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Correct answer: D — Oxaloacetate
Acetyl-CoA condenses with Oxaloacetate to form Citrate, which is the initial step of the TCA cycle. Oxaloacetate is the molecule that accepts the Acetyl group.
Q6. In the context of the TCA cycle, what is the fate of the carbon atoms derived from Acetyl-CoA?
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Correct answer: C — Oxidation and entry into the cycle to form CO2 and reducing equivalents
Acetyl-CoA enters the TCA cycle, undergoes oxidation, and is fully broken down to produce CO2, and crucially, generates NADH and FADH2 carriers.
Q7. The reduced coenzymes (NADH and FADH₂) generated during the TCA cycle primarily feed into which subsequent stage of aerobic respiration?
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Correct answer: B — Electron Transport System
NADH and FADH₂ carry high-energy electrons to the Electron Transport System (ETS) where the majority of ATP is generated.
Q8. Which enzyme in the TCA cycle catalyzes the formation of NADH from α-Ketoglutarate?
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Correct answer: B — α-Ketoglutarate dehydrogenase
The step involving the oxidative decarboxylation of α-Ketoglutarate to form Succinyl-CoA results in the reduction of NAD⁺ to NADH.
Q9. What is the main purpose of the FADH₂ produced during the TCA cycle?
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Correct answer: D — To supply electrons to the Electron Transport System
FADH₂ donates its electrons to the ETS, contributing to the proton gradient and subsequent ATP synthesis.
Q10. The primary function of the Electron Transport System (ETS) in aerobic respiration is to generate which of the following?
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Correct answer: B — ATP
The ETS uses the energy released from electron flow to pump protons, creating a proton gradient (chemiosmosis), which ultimately drives ATP synthesis via ATP synthase.
Q11. Which stage of aerobic respiration primarily occurs in the mitochondrial matrix?
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Correct answer: B — Krebs Cycle (TCA Cycle)
The Krebs Cycle (TCA Cycle) takes place in the mitochondrial matrix, where it generates the reduced coenzymes (NADH and FADH2) that feed into the Electron Transport System (which occurs on the inner membrane).
Q12. In which compartment of the mitochondrion does the TCA cycle take place?
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Correct answer: A — Mitochondrial matrix
The entire TCA cycle occurs within the mitochondrial matrix, where the necessary enzymes and substrates are located.
Q13. Which coenzyme generated during the TCA cycle acts as the primary electron donor to the Electron Transport System (ETS) in aerobic respiration?
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Correct answer: C — NADH
NADH (Nicotinamide adenine dinucleotide) and FADH₂ (Flavin adenine dinucleotide) are the reduced coenzymes generated during the TCA cycle. These molecules carry high-energy electrons that are subsequently passed down the Electron Transport System to generate ATP.
Q14. In the TCA cycle, which of the following molecules is directly oxidized to generate energy (in the form of NADH)?
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Correct answer: C — α-ketoglutarate
Succinate is oxidized to form Fumarate in the cycle, and the preceding step involves the oxidation of α-ketoglutarate to Succinyl-CoA, generating NADH. (Focusing on oxidation steps within the cycle).
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