Question

Match List-I with List-II

List-I (Enzyme Process) & List-II (Electron donor Requirement)
(A). Nitrite reductase & (I). NADH
(B). APS sulfotransferase & (II). NADPH
(C). Fatty acid synthesis & (III). Glutathione
(D). Nitrate reductase & (IV). Ferredoxin (Reduced)

Choose the correct answer from the options given below:

• (A) - (II), (B) - (IV), (C) - (III), (D) - (I)
• (A) - (III), (B) - (II), (C) - (IV), (D) - (I)
• (A) - (IV), (B) - (III), (C) - (II), (D) - (I)
• (A) - (III), (B) - (IV), (C) - (I), (D) - (II)

Hint:

Remember: - Nitrate Reductase uses NADH in the cytosol. - Nitrite Reductase uses Ferredoxin in the plastids/chloroplasts.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Many metabolic and assimilatory pathways in plants rely on specific cofactors and electron donors to reduce substrates into functional organic molecules.

Step 2: Detailed Explanation:
Let's pair each enzyme or metabolic process in List-I with its required electron donor in List-II:
- (A) Nitrite Reductase reduces nitrite ($\text{NO}_2^-$) to ammonium ($\text{NH}_4^+$) in the plastids.
This reaction requires six electrons, which are provided by reduced ferredoxin (IV) generated during the light reactions of photosynthesis.
- (B) APS Sulfotransferase is a key enzyme in the sulfate assimilation pathway.
It transfers a sulfonyl group from APS to an acceptor, a reaction that requires reduced glutathione (III) as an electron donor.
- (C) Fatty Acid Synthesis is an anabolic pathway that assembles carbon chains.
This process requires reducing power in the form of NADPH (II) to reduce intermediate keto groups.
- (D) Nitrate Reductase is a cytosolic enzyme that performs the first step of nitrogen assimilation, reducing nitrate ($\text{NO}_3^-$) to nitrite ($\text{NO}_2^-$).
This reaction requires two electrons, which are provided by NADH (I) generated during glycolysis.
This matching sequence corresponds to Option 3.

Step 3: Final Answer:
The correct match is (A) - (IV), (B) - (III), (C) - (II), (D) - (I).