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.
PDH & TCA cycle
Acetyl-CoA
Made from Pyruvate by Pyruvate dehydrogenase complex (PDH)
Pyruvate dehydrogenase complex (PDH) · irreversible — PDH & TCA cycle
Cofactors: TPP (thiamine, B₁), Lipoic acid, CoA (pantothenate, B₅), FAD (riboflavin, B₂), NAD⁺ (niacin, B₃)
Activated by: Pyruvate (inhibits PDH kinase); Ca²⁺ & insulin (activate PDH phosphatase → dephosphorylated, active E1)
Inhibited by: Acetyl-CoA; NADH; ATP (all activate PDH kinase → phosphorylated, inactive E1); Arsenite (binds lipoic acid)
Deficiency: PDH deficiency — neonatal lactic acidosis, neurologic defects; treat with a ketogenic diet (lysine, leucine) so fuel bypasses pyruvate
E1 pyruvate decarboxylase (TPP), E2 dihydrolipoyl transacetylase (lipoic acid, CoA), E3 dihydrolipoyl dehydrogenase (FAD, NAD⁺). Thiamine deficiency blocks it → pyruvate → lactate. Give thiamine BEFORE glucose.
Condition cards:Pyruvate dehydrogenase complex (PDHC) deficiency →
Becomes Citrate via Citrate synthase
Citrate synthase · irreversible — PDH & TCA cycle
Inhibited by: ATP; NADH; Citrate (product)
Acetyl-CoA + oxaloacetate → citrate. Citrate exported to the cytosol is the source of acetyl-CoA for fatty acid synthesis — and it inhibits PFK-1.