Learn / Metabolism

Metabolic pathways

Every FMK pathway as a clickable map. Pick one pathway to hammer it — next step, enzyme, regulator, cofactor, and the facts that get tested (NADPH and who needs it, rate-limiting steps, deficiencies) — or set it to all pathways for a mixed drill. Every answer says which enzyme and which pathway.

Pathway

PDH & TCA cycle · Mitochondrial matrix. Enzymes sit beside the arrows, ★ = rate-limiting, ⊕/⊖ = activators/inhibitors (toggle), −ATP +NADH = what the step spends and makes (toggle ⚡), dashed = allosteric signal, shaded bands = compartment. Drag to pan.

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PDH & TCA cycle

Succinyl-CoA

Made from α-Ketoglutarate by α-Ketoglutarate dehydrogenase complex

α-Ketoglutarate dehydrogenase complex · irreversible — PDH & TCA cycle

Cofactors: TPP (B₁), Lipoic acid, CoA, FAD, NAD⁺ → NADH, CO₂ released

Activated by: Ca²⁺

Inhibited by: Succinyl-CoA; NADH; ATP; Arsenite

Same five cofactors as PDH; same thiamine and arsenic vulnerability.

Becomes Succinate via Succinyl-CoA synthetase (succinate thiokinase)

Succinyl-CoA synthetase (succinate thiokinase) — PDH & TCA cycle

Cofactors: GDP → GTP (substrate-level)

Only substrate-level phosphorylation of the cycle. Succinyl-CoA is also the entry point for odd-chain fatty acids and Val/Ile/Met/Thr (propionyl-CoA → methylmalonyl-CoA → succinyl-CoA, needs B₁₂) and the start of heme synthesis.