NEET Biology: Photosynthesis and Respiration Practice Questions
15 free multiple-choice questions on Photosynthesis and 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 Photosynthesis and Respiration questions in the app →Q1. Photorespiration is an energy-wasting process that occurs when the enzyme Rubisco binds to which molecule in the presence of low CO₂ concentrations?
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Correct answer: C — O₂
Photorespiration occurs when Rubisco, instead of binding CO₂, binds O₂ on the same active site, leading to the emission of O₂ instead of CO₂.
Q2. The mechanism by which chemiosmosis functions is based on the differential flow of which type of ions across a membrane?
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Correct answer: D — Protons
The process relies on the movement of protons (H+) across a membrane to establish the gradient, which is the driving force for ATP synthesis.
Q3. What molecule acts as the immediate electron acceptor from Photosystem II as electrons move down the chain?
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Correct answer: A — Plastoquinone (PQ)
Following light absorption in PSII, the excited electrons are passed to the primary electron acceptor, which is typically Plastoquinone (PQ), which then carries the electrons to the next complex.
Q4. The C₄ pathway effectively concentrates CO₂ around which specific enzyme to maintain efficient carbon assimilation?
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Correct answer: C — RuBisCO
In C₄ plants, CO₂ is initially fixed by PEP carboxylase and then transported to the bundle sheath cells where CO₂ is concentrated around RuBisCO, reducing photorespiration.
Q5. Which of the following factors is the most limiting factor for the rate of photosynthesis in a closed system?
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Correct answer: A — Concentration of carbon dioxide
In a closed system where light and water are abundant, the concentration of carbon dioxide (CO₂) is often the limiting factor that determines the maximum rate of photosynthesis, as it is a reactant required for the Calvin cycle.
Q6. The C4 pathway involves the initial fixation of CO₂ by which initial enzyme in the mesophyll cells?
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Correct answer: A — Phosphoenolpyruvate carboxylase
In C4 plants, PEP carboxylase fixes CO₂ into a four-carbon compound (oxaloacetate), which is then transported to the bundle sheath cells for the Calvin cycle.
Q7. Which molecule acts as the final acceptor for electrons, indirectly setting up the conditions for chemiosmotic coupling in respiration?
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Correct answer: B — Oxygen
Oxygen acts as the final electron acceptor in the respiratory chain. Its involvement in the redox reactions drives the establishment of the proton gradient necessary for ATP production.
Q8. In the context of oxidative phosphorylation, the proton gradient is established by the action of which process?
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Correct answer: B — Electron Transport Chain (ETC)
The Electron Transport Chain (ETC) pumps protons (H⁺) from the mitochondrial matrix into the intermembrane space, creating the proton motive force (gradient).
Q9. The Chemiosmotic hypothesis primarily explains the mechanism for the synthesis of which molecule in cellular respiration?
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Correct answer: A — ATP
The Chemiosmotic hypothesis posits that the energy stored in the proton gradient across a membrane is used to drive the synthesis of ATP.
Q10. In C4 plants, the initial CO₂ fixation occurs in the mesophyll cells. The resulting four-carbon compound is transported to the bundle sheath cells where it is released. Which compound is typically used for transport in the C4 cycle?
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Correct answer: C — Malate
Malate (or aspartate) is the primary organic acid used for the transport of the fixed carbon from the mesophyll cells to the bundle sheath cells in C4 plants.
Q11. Which molecule acts as the initial electron donor for the light-dependent reactions during photophosphorylation in oxygenic photosynthesis?
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Correct answer: D — H₂O
Water (H₂O) is split during the light reactions, releasing electrons, protons, and oxygen. The electrons replace those lost by Photosystem II, initiating the flow of electrons that drives photophosphorylation.
Q12. What is the optimal temperature range for the rate of photosynthesis in most plants?
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Correct answer: A — 10°C to 20°C
Photosynthesis generally occurs most efficiently at moderate temperatures, typically between 20°C to 30°C for most plants.
Q13. Where does the process of photophosphorylation primarily occur in photosynthetic organisms like plants and cyanobacteria?
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Correct answer: D — Thylakoid membrane
Photophosphorylation occurs across the thylakoid membrane, which is embedded within the chloroplasts. This membrane contains the photosystems and electron transport chain components necessary for light-dependent reactions.
Q14. Which of the following is a primary consequence (loss) of photorespiration in photosynthetic organisms?
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Correct answer: C — Release of CO₂
Photorespiration results in the wasteful consumption of energy and the release of previously fixed carbon as CO₂, reducing the net production of sugars.
Q15. The absorption of light by chlorophyll is crucial for photosynthesis. What kind of light is primarily used by plants for photosynthesis?
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Correct answer: B — Visible light
Plants primarily utilize light in the visible spectrum (which includes red and blue wavelengths) for the process of photosynthesis.
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