KIVO Med
Fructose and galactose: entry routes, crossroads, and enzyme defects
Two hexoses enter energy metabolism through distinct steps, with clinically important points of failure.
- 25 explained questions
- 24 flashcards
- 130 estimated course minutes
Updated
What you will learn
- Distinguish dietary sources of fructose and galactose and their intestinal route.
- Describe fructose pathways in muscle, adipose tissue, and liver.
- Trace the hepatic pathway of galactose and its metabolic outputs.
- Relate each pathway to glycolysis, glycogen synthesis, and lipogenesis.
- Recognize inherited fructose and galactose enzyme defects and their clinical consequences.
Course outline
Two hexoses joining the glucose network
Fructose and galactose start from different food sources, cross the intestine, and reach shared energy crossroads.
12 min
Bring fructose into muscle and adipose tissue
In these tissues, hexokinase converts fructose into fructose 6-phosphate, a crossroads for glycolysis and glycogenesis.
12 min
Convert hepatic fructose into trioses
Four distinct reactions convert fructose into DHAP and G3P, joining glycolysis after consumption of two ATP.
20 min
Distinguish fructose excess, fructosuria, and hereditary intolerance
Massive intake and two enzyme deficiencies affect different points and differ in accumulated metabolite and severity.
18 min
From dietary lactose to hepatic galactose
Lactase releases galactose from lactose; liver converts it while preserving UDP sugars useful for biosynthesis.
14 min
The Leloir pathway, from galactose to glucose 6-phosphate
Four reactions phosphorylate galactose, exchange a uridyl group, epimerize the UDP sugar, and move a phosphate.
22 min
Connect each galactosaemia to its blocked step
GALT, epimerase, and galactokinase deficiencies raise galactosaemia but differ in accumulations and manifestations.
20 min
Compare pathways without confusing their crossroads
A final comparison connects sugar, tissue, first enzyme, connecting intermediate, and characteristic deficiency.
12 min
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