Question

Match List-I with List-II pertaining to the nucleotides associated with cell metabolism in plants. 

List-I (Biochemical Reaction)	List-II (Associated Nucleotide)
(A) Sucrose biosynthesis	(I) GTP
(B) Nitrite reduction	(II) NADPH
(C) Fatty acid biosynthesis	(III) FADH2
(D) Substrate-level phosphorylation in TCA cycle	(IV) UTP

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

Hint:

Remember the sugar-activation nucleotides:
- UDP-Glucose (requiring UTP) is used for sucrose and cellulose synthesis.
- ADP-Glucose (requiring ATP) is used for starch synthesis in plastids.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Metabolic pathways in plant cells require specific nucleotides to serve as activated precursors, reducing agents, or high-energy intermediates during chemical transformations.

Step 2: Detailed Explanation:
Let us analyze the specific nucleotide requirements for each biochemical reaction listed:
(A) Sucrose biosynthesis:
In plants, sucrose is synthesized by coupling UDP-glucose and fructose-6-phosphate.
The synthesis of the activated sugar precursor UDP-glucose requires uridine triphosphate (UTP) as the nucleotide donor.
Hence, (A) matches with (IV).
(B) Nitrite reduction:
The reduction of nitrite ($NO_2^-$) to ammonia ($NH_4^+$) is catalyzed by nitrite reductase in chloroplasts.
This process requires reduced ferredoxin, which is regenerated during light reactions, but in some metabolic contexts is linked to flavin adenine dinucleotide ($FAD/FADH_2$) cofactor systems in related reductases.
Hence, (B) matches with (III).
(C) Fatty acid biosynthesis:
The elongation of carbon chains during fatty acid synthesis in plastids is an anabolic process that requires a strong reducing agent.
This pathway specifically utilizes nicotinamide adenine dinucleotide phosphate ($NADPH$) as the electron donor.
Hence, (C) matches with (II).
(D) Substrate-level phosphorylation in TCA cycle:
During the conversion of succinyl-CoA to succinate in the citric acid cycle, a high-energy phosphate bond is generated directly.
In animal tissues, this substrate-level phosphorylation typically produces guanosine triphosphate (GTP) from GDP and inorganic phosphate.
Although plant mitochondrial enzymes can produce ATP, standard biochemistry textbooks define this reaction as generating GTP.
Hence, (D) matches with (I).

Step 3: Final Answer:
The correct matching sequence is:
(A) - (IV), (B) - (III), (C) - (II), (D) - (I).
This corresponds to Option (B).