Question

Which of the following statements are correct about photosynthesis
(A). Photosystem I has a greater number of a particular type of chlorophyll molecule called chlorophyll a
(B). Photosystem II is maximally activated at wavelengths shorter than 680 nm
(C). In photosystem I, NADPH is produced.
(D). Photosystem II is maximally activated at wavelengths larger than 680 nm
Choose the correct answer from the options given below:

• A. (A), (B) and (D) only.
• B. (A), (B) and (C) only.
• C. (A), (B), (C) and (D).
• D. (B), (C) and (D) only.

Hint:

A key distinction to remember: PSII (P680) initiates electron flow by splitting water and is sensitive to wavelengths \(\leq\) 680 nm. PSI (P700) is the terminal system in linear flow, leads to NADPH production, and can use light of wavelengths \(\leq\) 700 nm, including far-red light (>680 nm) which PSII cannot efficiently use.

Answer 1

The Correct Option is B

Step 1: Overview: This question tests understanding of photosynthesis' light-dependent reactions, focusing on Photosystem I (PSI) and Photosystem II (PSII) roles. Step 2: Analysis: (A) PSI has more chlorophyll a: Both systems have chlorophyll a, but PSI has a higher chlorophyll a to chlorophyll b ratio. This statement is considered correct. (B) PSII is activated by wavelengths shorter than 680 nm: PSII's reaction center (P680) absorbs light best at 680 nm. It's activated by wavelengths of 680 nm or less. This is correct. (C) NADPH production in PSI: PSI's high-energy electrons are passed to Ferredoxin-NADP\(^+\) reductase (FNR), which reduces NADP\(^+\) to NADPH. This statement is correct. (D) PSII is activated by wavelengths longer than 680 nm: This is incorrect. PSII's efficiency decreases beyond 680 nm. PSI (P700) uses longer wavelengths. Step 3: Conclusion: Statements (A), (B), and (C) are accurate. (D) is incorrect. The correct answer includes only (A), (B), and (C).