Question

Which of the following is not a product of light reaction of photosynthesis?

• A. ATP
• B. NADH
• C. NADPH
• D. Oxygen

Hint:

Products of the light reaction: \[ \boxed{ ATP + NADPH + O_2 } \] Remember: \[ \boxed{ NADP^{+} \longrightarrow NADPH } \] Do not confuse \(\mathbf{NADPH}\) (photosynthesis) with \(\mathbf{NADH}\) (cellular respiration).

Answer 1

The Correct Option is B

Concept: Photosynthesis occurs in two stages:

• Light reaction

• Dark reaction (Calvin cycle)
During the light reaction, solar energy is converted into chemical energy. The major products formed are \[ \boxed{ ATP,\;NADPH,\;O_2. } \] NADH is not produced during the light reaction.

Step 1: Understand the light reaction.
The light reaction takes place in the thylakoid membranes of chloroplasts. Its main functions are \[ \boxed{ \begin{aligned} &\text{Photolysis of water}\\ &\text{ATP synthesis}\\ &\text{Reduction of NADP}^{+}\text{ to NADPH} \end{aligned} } \] Oxygen is released as a by-product.

Step 2: Identify the products formed.
Products of the light reaction are \[ \boxed{ ATP,\; NADPH,\; O_2. } \] These products are utilized during the Calvin cycle for carbohydrate synthesis.

Step 3: Determine the incorrect option.
NADH is mainly involved in cellular respiration and is not produced in the light reaction of photosynthesis. Hence, \[ \boxed{\textbf{Option (B)}} \] is the correct answer.