3. • It is ketohexose and commonly known as
fruit sugar, as it occurs free in fruits.
• It is very sweet sugar, much sweeter than
sucrose and more reactive than glucose.
• It occurs as constituent of sucrose and
also of polysaccharide insulin
• It is laevorotatory and hence is also called
laevulose.
4. FRUCTOSE METABOLISM PATHWAYS
• There are three metabolic pathways
• Fructokinase (catabolic pathways)
• Hexokinase (catabolic pathway)
• Sorbitol pathway (fructose synthesis pathway)
•FRUCTOKINASE
• In liver, the cells contains glucokinase instead of hexokinase
and this enzyme phosphorylates only glucose thus, in liver
fructose metabolize instead by fructose the fructose one
phosphate pathway
5. •HEXOKINASE PATHWAY
• In muscle and adipose tissue fructose can be phosphorylated
by hexokinase which is capable of phosphorylating both
glucose and fructose to form fructose 6 phosphate
•SORBITOL PATHWAY
• It is also a fructose synthesis pathway.
6. •DEFECTS IN FRUCTOSE
METABOLISM
•ESSENTIAL FRUCTOSURIA
• Due to deficiency of enzyme hepatic fructokinase fructose is not converted into
fructose one phosphate this is an a symptomatic condition which excrete
fructose in urine.
•HEREDITARY FRUCTOSE INTOLERENCE
• This is because of absence of enzyme aldolesbe
• Hereditary fructose intolerance causes intracellular accumulation of fructose one
phosphate , severe hypoglycemia, vomiting, hepatic failure and jaundice
7. •MANNOSE
• Mannose is hexocarbon hydrate
• It si found in plants polysaccharide and animal glycoproteins
• It does not occurs freely in nature but it is widely distributed
in combination as the polysaccharide mannose.
• Its biomedical importance is that it is for the structure of
polysaccharides ‘
• It is an epimer of glucose and differs in orientation of H and
OH on carbon 2.
