Question

Which of the following is responsible for the production of oxygen during photosynthesis? 
A. Calvin cycle 
B. Photolysis of water 
C. Cyclic photophosphorylation 
D. Reduction of NADP+

• A. Calvin cycle
• B. Photolysis of water
• C. Cyclic photophosphorylation
• D. Reduction of NADP+

Hint:

Remember, the oxygen produced in photosynthesis comes from the photolysis of water, which occurs in the light reactions. The Calvin cycle, on the other hand, is responsible for fixing carbon and producing glucose but does not release oxygen.

Answer 1

The Correct Option is B

Photosynthesis is the process by which plants convert light energy into chemical energy in the form of glucose. It occurs in two main stages: the light reactions and the Calvin cycle (dark reactions). The light reactions take place in the thylakoid membranes of the chloroplasts, and they involve the capture of light energy by chlorophyll. This energy is used to produce ATP and NADPH, which are then used in the Calvin cycle to fix carbon and produce glucose. Now, let's break down the options: 1. A) Calvin cycle: The Calvin cycle, also known as the dark reactions or light-independent reactions, occurs in the stroma of the chloroplasts. It uses the products of the light reactions, namely ATP and NADPH, to fix carbon dioxide and form glucose. However, it does not directly produce oxygen. Oxygen is produced during the light reactions, not the Calvin cycle. 2. B) Photolysis of water: Photolysis of water is the process during the light reactions where water molecules are split into oxygen, protons (H\(^+\)), and electrons (e\(^-\)) by the energy absorbed from light. This reaction occurs in the thylakoid membranes and is crucial for the production of oxygen during photosynthesis. The oxygen atoms released in this process are the source of the oxygen gas that is released into the atmosphere as a byproduct of photosynthesis. The overall equation for photolysis is: \[ 2H_2O \xrightarrow{\text{light energy}} 4H^+ + 4e^- + O_2 \] This is the direct source of the oxygen produced during photosynthesis. 3. C) Cyclic photophosphorylation: In cyclic photophosphorylation, electrons flow in a cycle through the photosystem I, resulting in the production of ATP, but not NADPH or oxygen. Since no photolysis of water occurs in this process, oxygen is not produced. 4. D) Reduction of NADP+: The reduction of NADP+ to NADPH occurs during the light reactions, specifically in non-cyclic photophosphorylation. This process is important for the subsequent steps of the Calvin cycle, but it does not produce oxygen. Oxygen is produced during photolysis of water, not during the reduction of NADP+. Therefore, the correct answer is B) Photolysis of water, as this is the process directly responsible for the production of oxygen during photosynthesis.