24. Glycolysis and citric acid cycle contribute precursors to many biosynthesis pathway in plants. column X lists names of the precursors and column Y lists the product synthesized.
Column X Column Y
A. Hexose phosphate (i) Aspartate
B. Pyruvate (ii) Alanine
C. Pentose phosphate (iii) Cellulose
D. Oxaloacetate (iv) Nucleotides
Which one of the following options represents the correct match between column X and Y?
(1) A-ii, B-iii, C-i and D-iv (2) A-iii, B-ii, C-iv and D-i
(3) A-iv, B-i, C-iii and D-ii (4) A-i, B-ii, C-iii and D-iv
Introduction
The central metabolic pathways of glycolysis and the citric acid cycle generate key intermediates that serve as precursors for the biosynthesis of many essential biomolecules in plants. These processes sustain plant growth by linking energy metabolism with structural and functional synthesis.
Detailed Explanation of Each Option
(A) Hexose phosphate → (iii) Cellulose
Hexose phosphate, particularly glucose-6-phosphate, is polymerized to form cellulose, the major structural carbohydrate in plant cell walls.
(B) Pyruvate → (ii) Alanine
Pyruvate is directly transaminated to form the amino acid alanine, making it the key precursor in this pathway.
(C) Pentose phosphate → (iv) Nucleotides
The pentose phosphate pathway generates ribose-5-phosphate, the five-carbon sugar essential for nucleotide (and nucleic acid) synthesis.
(D) Oxaloacetate → (i) Aspartate
Oxaloacetate undergoes transamination to synthesize aspartate, a key amino acid involved in further biosynthetic pathways.
Option Analysis
Option 1 (A-ii, B-iii, C-i, D-iv):
Incorrect. Assigns hexose phosphate to alanine and pyruvate to cellulose, which do not align with metabolic pathways.
Option 2 (A-iii, B-ii, C-iv, D-i):
Correct. Matches are consistent with plant biosynthetic pathways: Cellulose from hexose phosphate, alanine from pyruvate, nucleotides from pentose phosphate, and aspartate from oxaloacetate.
Option 3 (A-iv, B-i, C-iii, D-ii):
Incorrect. Assigns hexose phosphate to nucleotides, which is not the direct pathway, and mismatches other pairs.
Option 4 (A-i, B-ii, C-iii, D-iv):
Incorrect. Assigns hexose phosphate to aspartate, which is not biochemically accurate.
Summary Table
| Precursor (Column X) | Product (Column Y) | Explanation |
|---|---|---|
| Hexose phosphate | Cellulose (iii) | Glucose unit for cellulose synthesis |
| Pyruvate | Alanine (ii) | Via transamination |
| Pentose phosphate | Nucleotides (iv) | Provides ribose phosphate for nucleic acids |
| Oxaloacetate | Aspartate (i) | Via transamination |
The correct option—Option 2—reflects the actual metabolic flow from central intermediates to major biosynthetic products in plants, linking core metabolism to vital biosynthetic functions.
