Subtopic: Fundamentals of Downstream processing (chromatography, filtration)
Question Statement:
Which one of the following options represents the products of light reactions of
photosynthesis in plants?
Options:
(A) O2/NADH/H2
(B) O2/NADP+/CO2
(C) O2/NADPH/ATP
(D) O2/NADP+/ATP
Official Answer Key:
C
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2026 Q.25)**
**1. Governing Concept**:
- **Topic**: Plant Physiology & Photosynthetic Light Reactions (Z-Scheme)
- In the thylakoid membrane, light reactions involve non-cyclic photophosphorylation driven by Photosystem II (PSII) and Photosystem I (PSI):
- **Photolysis of Water at PSII**: $2\text{H}_2\text{O} \xrightarrow{\text{OEC}} \text{O}_2 + 4\text{H}^+ + 4e^-$, generating **$\text{O}_2$** as a byproduct.
- **Proton Translocation**: Powers ATP synthase to photophosphorylate ADP into **ATP**.
- **Terminal Reduction at PSI**: Ferredoxin-$\text{NADP}^+$ reductase reduces $\text{NADP}^+$ to **NADPH**.
- The net products of the light reactions that enter the stroma for the Calvin cycle are **ATP, NADPH, and $\text{O}_2$**.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: Lists glucose, which is synthesized during the light-independent Calvin cycle in the stroma, not the light reactions.
- **Option (B) is INCORRECT**: Lists $\text{NADP}^+$ (reactant) rather than NADPH (reduced product).
- **Option (C) [ATP, NADPH, and O2] is CORRECT**: The three primary products of thylakoid light-dependent non-cyclic electron transport.
- **Option (D) is INCORRECT**: Confuses light reaction products with carbon fixation intermediates.
**3. Final Answer**:
- **Correct Choice**: **C**
Practice This in Real CBT Exam Interface
Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.