What is Krebs Cycle in NEET PG?

Krebs Cycle is a topic in the Biochemistry syllabus of NEET PG. It carries a weight of 3% in the exam. Our notes cover the key concepts, formulas, and problem-solving approaches you need to master this topic.

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Krebs Cycle

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

Krebs Cycle (Citric Acid Cycle) — Key Facts for NEET PG Core concept: Aerobic oxidation of acetyl-CoA to produce NADH, FADH₂, and GTP High-yield point: Each acetyl-CoA generates 3 NADH, 1 FADH₂, and 1 GTP (≈12.5 ATP per cycle) ⚡ Exam tip: Remember the 8-step cycle — enzymes and intermediates are frequently asked

🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

Krebs Cycle — NEET PG Study Guide Overview: The citric acid cycle operates in the mitochondrial matrix and is the central hub of carbohydrate, fat, and protein metabolism Key intermediates: Citrate → Isocitrate → α-Ketoglutarate → Succinyl-CoA → Succinate → Fumarate → Malate → Oxaloacetate Key enzymes: Citrate synthase, aconitase, isocitrate dehydrogenase (rate-limiting step), α-ketoglutarate dehydrogenase, succinyl-CoA synthetase, succinate dehydrogenase, fumarase, malate dehydrogenase Regulatory enzymes: Isocitrate dehydrogenase and α-ketoglutarate dehydrogenase (allosteric regulation by ADP/AMP activates, ATP/NADH inhibits) Energy yield: 2 acetyl-CoA → 2 GTP + 6 NADH + 2 FADH₂ = ~24 ATP per glucose (including oxidative phosphorylation) Anaplerotic reactions: Pyruvate carboxylase, glutamate dehydrogenase replenish OAA; this is clinically relevant in fasting states Clinical correlation: Thiamine deficiency impairs α-ketoglutarate dehydrogenase → Wernicke encephalopathy

🔴 Extended — Deep Study (3mo+)

Comprehensive coverage forstudents on a longer study timeline.

Krebs Cycle — Comprehensive NEET PG Notes Full coverage: Detailed intermediate-by-intermediate study of all 8 steps with enzyme mechanisms Detailed theory: Each step with substrates, products, enzymes, and cofactors (TPP, lipoic acid, CoA, FAD, NAD⁺) Regulatory sites: Allosteric inhibition by ATP/NADH, calcium activation of isocitrate dehydrogenase Connection to other cycles: Links with gluconeogenesis (OAA → PEP), transamination (amino acid synthesis), and fatty acid synthesis ( citrate export) Problem-solving: Previous year NEET questions on ATP yield calculation, enzyme deficiencies, and anaplerotic reactions Common mistakes: Confusing FADH₂ yield vs NADH yield; forgetting that 1 cycle = 1 acetyl-CoA (glucose gives 2 acetyl-CoA)

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