NEET Biology: Respiration Practice Questions
15 free multiple-choice questions on 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 Respiration questions in the app →Q1. What is the net total number of ATP molecules generated during the complete aerobic respiration of one molecule of glucose?
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Correct answer: A — 36
Aerobic respiration of one glucose molecule yields approximately 36 to 38 ATP molecules, depending on the exact method used for ATP synthesis (the standard modern estimate is often 38, incorporating proton gradient effects).
Q2. In aerobic respiration, approximately how many ATP molecules are generated directly by the electron transport chain (ETC) if 1 NADH and 1 FADH2 enter the chain?
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Correct answer: A — 7
NADH generates approximately 2.5 ATP (via oxidative phosphorylation) and FADH2 generates approximately 1.5 ATP. If we consider the direct input to the proton gradient, the yield is based on the relative input. In simplified terms focusing on the energy potential: NADH yields about 2 ATP and FADH2 yields about 1 ATP (or 2 ATP depending on the exact model; focusing on the maximum potential yield derived from the carriers). A direct count focusing on the total potential energy derived from these carriers leads to a higher number than simple substrate-level phosphorylation count.
Q3. Which characteristic best describes metabolic pathways that are both catabolic and anabolic?
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Correct answer: A — amphibolic
Amphibolic pathways are those that serve both catabolic (breaking down) and anabolic (building up) functions, making them amphibolic.
Q4. What is the immediate end product of the anaerobic breakdown of pyruvate in the absence of oxygen (fermentation)?
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Correct answer: C — Lactate
When oxygen is scarce, pyruvate is converted into lactate (lactic acid) to regenerate NAD+ for continued glycolysis.
Q5. The respiratory membrane in the lungs is composed of which two main layers?
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Correct answer: B — Alveolar epithelium and capillary endothelium
The respiratory membrane consists of the thin layer of alveolar epithelium and the thin layer of capillary endothelium, which is the site of gas exchange.
Q6. 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.
Q7. 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.
Q8. The initial phase of glycolysis is known as the energy investment phase. How many molecules of ATP are consumed in this initial phase?
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Correct answer: D — 4 ATP
The energy investment phase requires the input of 2 molecules of ATP to destabilize the glucose molecule for subsequent cleavage.
Q9. 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.
Q10. Which stage of aerobic respiration, after glycolysis, is primarily responsible for generating the vast majority of ATP through oxidative phosphorylation?
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Correct answer: C — Electron Transport Chain (ETC)
While glycolysis produces a small amount of ATP directly, the Electron Transport Chain (ETC) and oxidative phosphorylation, driven by the carriers generated in the preceding stages, produce the bulk of the ATP.
Q11. Where does the process of glycolysis primarily occur in a eukaryotic cell?
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Correct answer: B — Cytoplasm
Glycolysis is the metabolic pathway that breaks down glucose into pyruvate, and it occurs in the cytosol (cytoplasm) of the cell, not inside the mitochondria.
Q12. 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.
Q13. What is the total theoretical yield of ATP molecules generated from the complete aerobic respiration of one molecule of glucose (starting from glycolysis)?
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Correct answer: D — 32
Aerobic respiration yields a total of approximately 32 ATP molecules from the complete breakdown of one molecule of glucose, derived from glycolysis, the Krebs cycle, and oxidative phosphorylation.
Q14. Which substance is typically produced as a byproduct during alcoholic fermentation in yeast?
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Correct answer: D — Ethanol
Alcoholic fermentation, which occurs in yeast, results in the production of ethanol (alcohol) and carbon dioxide.
Q15. Which part of the respiratory system is responsible for the mechanical process of breathing (inhalation and exhalation)?
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Correct answer: B — Diaphragm
The diaphragm is the principal muscle responsible for changing the volume of the thoracic cavity, which drives the inhalation and exhalation process.
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