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.
Carbohydrate digestion & absorption
FRUCTOSE
Made from At the brush border: maltose, α-limit dextrins, lactose, sucrose by SUCRASE-isomaltase (brush border) — sucrose → glucose + fructose
SUCRASE-isomaltase (brush border) — sucrose → glucose + fructose · irreversible — Carbohydrate digestion & absorption
Deficiency: Sucrase-isomaltase deficiency — congenital (rare, but prevalent among Inuit people of Greenland) or acquired after small-intestinal inflammation; the same GI picture as lactose intolerance
Condition cards:Sucrose intolerance (sucrase-isomaltase deficiency) →
Becomes Monosaccharides inside the enterocyte via GLUT-5 — FACILITATED diffusion only
GLUT-5 — FACILITATED diffusion only — Carbohydrate digestion & absorption
Fructose has no active transporter, which is why a large fructose load saturates absorption and causes osmotic diarrhoea in otherwise normal people.