Photosynthesis Quiz - CBSE Class 12 Biology

Free practice quiz: Photosynthesis (CBSE Class 12 Biology). 20 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. What is the primary product of the light-dependent reactions of photosynthesis?

   1. Glucose
   2. ATP and NADPH
   3. Oxygen
   4. Carbon dioxide
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   Answer: B. ATP and NADPH

   The light-dependent reactions use light energy to generate ATP and NADPH, which are then used in the light-independent reactions to produce glucose.

2. Explain photorespiration and its impact on photosynthetic efficiency.

   1. A process that enhances CO2 fixation
   2. A process that increases ATP production
   3. A wasteful process that competes with carbon fixation
   4. A process that improves water use efficiency
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   Answer: C. A wasteful process that competes with carbon fixation

   Photorespiration is a process where RuBisCo binds with oxygen instead of carbon dioxide, leading to a net loss of energy and reduced photosynthetic efficiency.

3. Explain the chemiosmotic hypothesis in relation to ATP synthesis during photosynthesis.

   1. ATP is synthesized directly by light
   2. ATP is synthesized through substrate-level phosphorylation
   3. ATP synthesis is driven by a proton gradient across the thylakoid membrane
   4. ATP synthesis is independent of electron transport
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   Answer: C. ATP synthesis is driven by a proton gradient across the thylakoid membrane

   The chemiosmotic hypothesis explains how the proton gradient generated during electron transport drives ATP synthesis via ATP synthase in the thylakoid membrane.

4. Explain the role of photolysis in the light-dependent reactions.

   1. It reduces NADP+
   2. It generates ATP
   3. It splits water molecules to release electrons, protons, and oxygen
   4. It fixes carbon dioxide
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   Answer: C. It splits water molecules to release electrons, protons, and oxygen

   Photolysis, or the splitting of water molecules, provides electrons to replenish those lost by photosystem II, releasing oxygen as a byproduct.

5. Explain the concept of quantum efficiency in photosynthesis and its importance in understanding photosynthetic limitations.

   1. It is irrelevant
   2. It is the efficiency of light absorption and conversion to chemical energy
   3. It measures the rate of respiration
   4. It is constant irrespective of conditions
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   Answer: B. It is the efficiency of light absorption and conversion to chemical energy

   Quantum efficiency measures how efficiently absorbed photons are converted into chemical energy, providing insights into photosynthetic limitations under various conditions.

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