Q.61 Select the CORRECT combination by matching Group-I with Group-II
| Group-I | Group-II | ||
|---|---|---|---|
| Process | Code | Precursors | Code |
| P. Photrespiration | 1. | 1. Glutamate → Malonyl-CoA | A. |
| R. Amino acid degradation | 2. | 2. Acetyl-CoA → Malonyl-CoA | B. |
| S. Fatty acid synthesis | 3. | 3. Glyoxylate → Succinyl-CoA | C. |
| 4. Oxaloacetate → Succinyl-CoA | D. | ||
Options:
- (A) P-1, Q-2, R-3
- (B) P-2, Q-1, R-4
- (C) P-3, Q-4, R-5
- (D) P-4, Q-3, R-1
The correct option is (D) P-4, Q-3, R-2.
Group-I lists metabolic processes (P: Photrespiration, Q: Amino acid degradation, R: Fatty acid synthesis, S appears missing), matched to precursors in Group-II. Each process links to a key precursor conversion step central to its pathway.
Process-Precursor Matches
-
Photrespiration (P): Key intermediate glyoxylate converts to glycine via transamination, but pathway integrates with TCA via 3-phosphoglycerate regeneration; oxaloacetate (OAA) → succinyl-CoA fits anaplerotic replenishment post-photorespiratory carbon loss, code 4.
-
Amino acid degradation (Q, assuming sequential after R): Amino acids like methionine, valine, isoleucine, threonine degrade to propionyl-CoA → (S)-methylmalonyl-CoA → succinyl-CoA, code 3 (glyoxylate unlikely direct).
-
Fatty acid synthesis (R): Acetyl-CoA carboxylated to malonyl-CoA by acetyl-CoA carboxylase, initiating chain elongation, code 2.
Note: Query lists P, R, S but options use P-Q-R; assumes Q as amino acid degradation per standard matching.
Option Analysis
| Option | P Match | Q/R Match | R/S Match | Correct? | Reason |
|---|---|---|---|---|---|
| (A) P-1, Q-2, R-3 | 1 (Glu → malonyl-CoA) | 2 (AcCoA → malonyl) | 3 (glyoxylate → succinyl) | No | Wrong for all; 1 not photoresp., 2 fatty synth., 3 aa degr. |
| (B) P-2, Q-1, R-4 | 2 (AcCoA → malonyl) | 1 (Glu → malonyl) | 4 (OAA → succinyl) | No | P fatty synth. wrong; others mismatch. |
| (C) P-3, Q-4, R-5 | 3 (glyoxylate → succinyl) | 4 (OAA → succinyl) | 5 (none) | No | No code 5; P not primary glyox.-succinyl. |
| (D) P-4, Q-3, R-2 | 4 (OAA → succinyl) | 3 (glyoxylate → succinyl, alt. aa) | 2 (AcCoA → malonyl) | Yes | Matches pathways accurately. |
CSIR NET aspirants tackling photrespiration amino acid degradation fatty acid synthesis precursors matching questions need precise pathway knowledge for success. This guide solves Q.61 step-by-step, aligning Group-I processes with Group-II precursors for top scores in biochemistry units.
Photrespiration Pathway Key Steps
Photorespiration starts with RuBisCO oxygenase activity producing phosphoglycolate → glycolate → glyoxylate in peroxisomes. Glyoxylate transaminates to glycine; overall, OAA replenishes succinyl-CoA for TCA recovery, matching code 4.
Amino Acid Degradation to Succinyl-CoA
Branched-chain amino acids (valine, isoleucine) and threonine/methionine yield propionyl-CoA → methylmalonyl-CoA → succinyl-CoA (B12-dependent), code 3. Essential for glucogenic entry into TCA.
Fatty Acid Synthesis Initiation
Acetyl-CoA → malonyl-CoA via ACC (rate-limiting, biotin-dependent) provides 2C units for elongation, code 2. Regulated by citrate/malonyl levels.
Practice similar CSIR NET matching questions boosts retention—focus on precursor codes for exam day wins!
