GTP Synthesis in Citric Acid Cycle — NEET Biology
✅ Asked in NEET 2024Identify the step in tricarboxylic acid cycle, which does not involve oxidation of substrate. NEET 2024
Identify the step in tricarboxylic acid cycle, which does not involve oxidation of substrate. NEET 2024
Number of substrate-level phosphorylations in one turn of the TCA cycle is: NEET 2020
Answer & NCERT explanation
Correct answer: C — Succinyl-CoA → Succinic acid
The conversion of succinyl-CoA to succinic acid does not involve oxidation. Instead, it involves substrate-level phosphorylation where the high-energy thioester bond is cleaved to produce GTP (equivalent to ATP). The other options involve oxidation reactions that reduce NAD+ or FAD.
Read more NCERT concept on the PYQ
In the remaining steps of citric acid cycle, succinyl-CoA is oxidised to OAA allowing the cycle to continue. During the conversion of succinyl-CoA to succinic acid a molecule of GTP is synthesised. This is a substrate level phosphorylation. In a coupled reaction GTP is converted to GDP with the simultaneous synthesis of ATP from ADP. Also there are three points in the cycle where NAD+ is reduced to NADH + H+ and one point where FAD+ is reduced to FADH2. The continued oxidation of acetyl CoA via the TCA cycle requires the continued replenishment of oxaloacetic acid, the first member of the cycle. In addition it also requires regeneration of NAD+ and FAD+ from NADH and FADH2 respectively. The summary equation for this phase of respiration may be written as follows:
In the citric acid cycle, succinyl-CoA is converted to succinic acid through a reaction catalyzed by succinyl-CoA synthetase, which produces GTP (or ATP) directly. This is substrate-level phosphorylation, different from oxidative phosphorylation. Students often confuse this step and think oxidation occurs here, but the key is that energy is captured as GTP through direct phosphorylation, not through electron transport. Remember: succinyl-CoA → succinic acid = GTP synthesis (substrate-level), while the actual oxidation steps in the cycle produce NADH and FADH₂. NTA has tested this distinction twice because it tests whether students understand the two different ATP-generating mechanisms in cellular respiration.
What does NCERT say about remaining steps citric acid?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
88/90MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.