09 Fructose and Galactose

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Absorption

• monosaccharides

Fructose

• table sugar
• fructose can be metabolized and feed into glycolysis

• fructokinase add phosphate from ATP
• aldolase B splits F1P to 2 3C molecules

• fructose enter pathway beyond rate limiting step, faster than either glucose/galactose

• hexokinase can convert fructose to F6P (step 2)

Essential Fructosuria

Hereditary Fructose Intolerance

• no aldolase
• fructose continuously converted to F1P, using up ATP

• need ATP for gluconeogenesis and glycogen breakdown

• no fructose from breast milk
• wean from breast milk, start fructose

Polyol

• sorbitol converted to fructose

• diabetes locaitons

Galactose

• G1P intermediate in glycogen synthesis, can be used for glycogen synthesis or converted to G6P

Classic Galactosemia

• GALT
• G1P builds up in liver and leads to liver damage, also deplete ATP supply

• also causes cataracts

• galactose in milk

Galactokinase Deficiency

• Galactose not converted to G1P, milder symptoms, no depletion of phosphate and no trapping in liver
• young child with vision problems