Kindly provide 15 Waec/gce/neco past questions on photosynthesis light and dark stages reactions with their answers

Answer 1

Sure! Below are 15 past questions related to the light and dark stages of photosynthesis along with their answers. These questions are designed to reflect the usual style of WAEC, GCE, and NECO examinations.

Questions and Answers

1. Question: What is the primary function of the light-dependent reactions in photosynthesis?

   • Answer: To convert solar energy into chemical energy in the form of ATP and NADPH.

2. Question: In which part of the chloroplast do the light-dependent reactions occur?

   • Answer: In the thylakoid membranes.

3. Question: What are the main products of the light-dependent reactions?

   • Answer: ATP, NADPH, and oxygen.

4. Question: What is the role of chlorophyll in photosynthesis?

   • Answer: Chlorophyll absorbs light energy, which excites electrons and initiates the light-dependent reactions.

5. Question: What is the name of the cycle that represents the dark stage (Calvin Cycle) of photosynthesis?

   • Answer: The Calvin-Benson Cycle.

6. Question: During the dark reactions, what molecule is fixed to form glucose?

   • Answer: Carbon dioxide (CO₂).

7. Question: What is the energy currency used in the dark reactions of photosynthesis?

   • Answer: ATP is used to provide energy, while NADPH provides reducing power.

8. Question: In the absence of sunlight, can plants still perform photosynthesis? Explain.

   • Answer: No, because the light-dependent reactions require light to produce ATP and NADPH, which are necessary for the dark reactions.

9. Question: Which enzyme is crucial for fixing carbon dioxide during the Calvin Cycle?

   • Answer: Rubisco (ribulose bisphosphate carboxylase/oxygenase).

10. Question: What is produced as a by-product of the light-dependent reactions?

    • Answer: Oxygen (O₂) is released as a by-product.

11. Question: In the dark reactions, what is regenerated to continue the cycle?

    • Answer: Ribulose bisphosphate (RuBP) is regenerated.

12. Question: Name one environmental factor that can affect the rate of photosynthesis.

    • Answer: Light intensity, carbon dioxide concentration, or temperature.

13. Question: How do the light-dependent and light-independent reactions of photosynthesis relate to each other?

    • Answer: The ATP and NADPH produced in the light-dependent reactions are used as energy sources in the light-independent reactions (Calvin Cycle).

14. Question: Describe the role of electron transport chains in photosynthesis.

    • Answer: Electron transport chains facilitate the transfer of electrons and contribute to the generation of a proton gradient, which is used to produce ATP.

15. Question: Why is photosynthesis considered an endothermic process?

    • Answer: Because it absorbs energy (in the form of sunlight) to convert carbon dioxide and water into glucose and oxygen, indicating that energy is needed for the reaction.

These questions cover the fundamental concepts of photosynthesis, specifically focusing on the light and dark reactions.