09 Fructose and Galactose

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