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.
Lipolysis, carnitine shuttle & β-oxidation
Fatty acyl-CoA (matrix)
Made from Acylcarnitine by Carnitine-acylcarnitine translocase → CPT II (inner membrane)
Carnitine-acylcarnitine translocase → CPT II (inner membrane) — Lipolysis, carnitine shuttle & β-oxidation
Cofactors: Carnitine regenerated
Deficiency: CPT II deficiency (muscle isoform, adult) — exercise/fasting/cold-induced myalgia, rhabdomyolysis, myoglobinuria, ↑CK, long-chain acylcarnitines high; infantile form has cardiomyopathy
CPT II regenerates acyl-CoA inside the matrix.
Condition cards:CPT II deficiency →
Made from Acetyl-CoA (+ acyl-CoA −2C) by Repeat until the chain is gone
Repeat until the chain is gone — Lipolysis, carnitine shuttle & β-oxidation
Palmitate: 7 rounds → 8 acetyl-CoA + 7 NADH + 7 FADH₂ ≈ 106 ATP net. Odd-chain fats end as propionyl-CoA → succinyl-CoA (biotin, B₁₂) — the only glucogenic bit of a fatty acid.
Becomes trans-Δ²-Enoyl-CoA via Acyl-CoA dehydrogenase (VLCAD / LCAD / MCAD / SCAD by chain length)
Acyl-CoA dehydrogenase (VLCAD / LCAD / MCAD / SCAD by chain length) — Lipolysis, carnitine shuttle & β-oxidation
Cofactors: FAD → FADH₂
Deficiency: MCAD deficiency — most common FAO disorder (AR): fasting/illness-triggered hypoketotic hypoglycemia, vomiting, lethargy, hepatomegaly, sudden death; ↑C8 octanoylcarnitine on newborn screen; avoid fasting, IV dextrose
First oxidation. MCAD handles C6–C10; VLCAD > C14. FADH₂ goes to ETF → CoQ.
Condition cards:MCAD deficiency →VLCAD deficiency →SCAD deficiency →Jamaican vomiting sickness (hypoglycin toxicity) →