10/6 Carb Metabolism Disorders Flashcards
path of fructose from intestines to hepatocytes
intestinal lumen —GLUT5—> enterocytes —GLUT2—> hepatic portal vein —GLUT2—> hepatocyte
path of galactose from intestines to hepatocytes
intestinal lumen —SGLT1—> enterocytes —GLUT2—> hepatic portal vein —GLUT2—> hepatocyte
what happens to fructose after entering the liver
converted to fructose 1 phosphate by fructokinase
reqs 1 ATP
what happens to galactose after entering the liver
converted to galactose 1-phosphate, requires 1 ATP
galactokinase
two fructose metabolism disorders
essential fructosuria (benign) hereditary fructose intolerance (severe)
essential fructosuria
AR mutation in fructokinase, accumulation of fructose, benign, peed out
herediatary fructose intolerance
AR mutation of hepatic fru-1-P-aldolaseB, toxic accumulation of F1P, vomiting/lethargy/severe hypoglucemia. depletes intercellular phosphate pools and therefore ATP pool, so it inhibits gluconeogenesis and glycogenolysis
two galactose metabolism disorders
classical galactosemia (severe) nonclassical galactosemia (not severe)
classical galactosemia
AR deficiency in Gal 1-P uridyltransferase, results in Gal 1-P buildip and galactose in blood/urine
after birth: feeding difficulties, vomiting, hepatosplenomegaly, mental retardation, cataracts, glycosuria, aminoaciduria
nonclassical galactosemia
AR deficiency in galactokinase, buildup of galactose in blood and tissues, galactitol can accumulate in lens –> cataracts, not as severe as classical
what does sorbitol dehydrogenase do
converts sorbitol to d-fructose
what happens to excess glucose
converted to fructose, with sorbitol as intermediate
what happens when you have increased levels of sorbitol
some tissues have relatively lower amounts of sorbitol dehydrogenase, sorbitol buildup fucks up osmotic balance, cell damage
linked to diabetic retinopathy, cataracts, peripheral neuropathy
other names for pentose phosphate pathway
hexose monophosphate shunt
phosphogluconate pathway
pentose phosphate pathway 2 main points
1) generates NADPH for rxns requiring reducing equivalents
2) generates ribose 5-phosphate for nucleotide biosynthesis
two stages of pentose phosphate pathway
1) oxidative (makes 2 mols of NADPH per oxidized G6P), regulated enzyme is G6P dehydrogenase (NADPH: feedback inhibition)
2) nonoxidative (makes ribose 5-P and converts unused intermediates to glycolytic pathway intermediates)
G6P dehydrogenase deficiency
most common enzymatic deficiency in humans, X-linked recessive, cannot deal with increased oxidative stress from infections, some drugs, fava beans. ROS/denatured hemoglobin –> compromised membrane intergrity –> hemolysis, jaundice
normal fxn of G6P dehydrogenase
the NADPH produced SHOULD control levels of reduced glutathione in cell, reduced glutathione is responsible for controlling oxidative stress in cells.
