Question

Given below are two statements :
Statement (I) : During photosynthesis, light energy is used to produce ATP and NADPH during the light-dependent reactions.
Statement (II) : ATP and NADPH produced in the light-dependent reactions are used to break down glucose into carbon dioxide and water during light-independent reactions.
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are true.
• B. Both Statement (I) and Statement (II) are false.
• C. Statement (I) is true but Statement (II) is false.
• D. Statement (I) is false but Statement (II) is true.

Hint:

Remember the metabolic flow of photosynthesis:
- Light Reactions $\rightarrow$ Light energy is captured to make ATP and NADPH (energy carriers).
- Dark Reactions (Calvin Cycle) $\rightarrow$ ATP and NADPH are consumed to fix $\text{CO}_2$ and synthesize sugars (energy storage).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Photosynthesis is divided into two metabolic phases: the light-dependent reactions (which capture solar energy) and the light-independent reactions (which fix carbon dioxide into sugars).

Step 2: Detailed Explanation:
Let us analyze both statements individually:
Statement (I): "During photosynthesis, light energy is used to produce ATP and NADPH during the light-dependent reactions."
This statement is correct.
In the thylakoid membranes, chlorophyll pigments absorb light energy to drive the transport of electrons from water to $NADP^+$, producing oxygen and NADPH.
This electron flow also generates a proton gradient across the membrane that powers ATP synthase to produce ATP.
Statement (II): "ATP and NADPH produced in the light-dependent reactions are used to break down glucose into carbon dioxide and water during light-independent reactions."
This statement is incorrect.
During the light-independent reactions (the Calvin cycle occurring in the stroma), the chemical energy stored in ATP and NADPH is used to *synthesize* high-energy carbohydrates (such as glucose) from inorganic carbon dioxide ($\text{CO}_2$).
It is a carbon-fixing, anabolic pathway, not a catabolic pathway that breaks down glucose.
The breakdown of glucose into carbon dioxide and water to release energy is called cellular respiration, which is a completely different pathway.
Therefore, Statement (I) is true, and Statement (II) is false.

Step 3: Final Answer:
Statement (I) is true, but Statement (II) is false.
This corresponds to Option (C).