Metabolism of other sugars Flashcards
in the mouth, alpha-amylase –>
cleaves non reducing esnds of polysaccs into di and trisaccs
maltose and maltotriose and a little glucose
maltose and maltotriose
2 or 3 glucoses connected by alpha1,4 linkages
alpha glucosidase
further digests maltose and maltotriose to glucose
brush border amylases
sucrase and lactase and trehalase
alpha-dextrinase
cleaves alpha1,6 linkages in amylopectin and glycogen
cellulose
indigestible plant carbohydrate –> insoluble fiber
adds bulk to feces and helps food pass more quickly through stomach and intestine
beta1,4 linked glucoses which humans cannot break
soluble fiber
oat bran, barley, nuts, seeds, beans etc
may help lower cholesterol
beta 1,4 and 1,3 linked glucose with galactose and galactuonic acid polymers that are indigestible by ours, but can be by bacteria
legume oligosaccharides
alpha linked galactoses that cannot be broken by humans
but can be by bacteria
sucralose (splenda)
modified sucrose
C4 on glucose and C1/6 on fructose have Cl- atoms replacing OH
not digestible anymore
divisions of microflora
bacteroidetes and firmicutes
obese people have more firmicutes –> might allow to derive more calories from the food they eat
link between toll-like receptor 5 (TLR5) and metabolic syndrome
combines to flagella of motile bacteria for an immune response
knockedout mice –> obese compared to not
fructose metabolism in extrahepatic tissue
enzyme = hexokinase (higher Km for fructose then glucose)
fructose –> F6P –> glycolysis
fructose concentration has to be high otherwise little fructose will be trapped in cell
fructose metabolism in liver
enzyme = fructokinase
fructose –> F1P (trapping fructose in cell)
enzyme = F1P aldolase (aldolase B)
F1P –> glyceraldehyde + DHAP
enzyme = triose kinase
Glyceraldehyde –> G3P
G3P and DHAP –> glycolysis
fructosuria
(-) fructokinase
cannot trap fructose in liver cells –> high fructose levels in blood –> might be excreted into urine
benign condition
fructose intolerance (fructosemia)
(-) fructose-1P aldolase
fructose is trapped but now can no longer create glycolytic intermediates
liver damage
restrict fructose