10/6 Carb Metabolism Disorders

Question 1

path of fructose from intestines to hepatocytes

Answer 1

intestinal lumen —GLUT5—> enterocytes —GLUT2—> hepatic portal vein —GLUT2—> hepatocyte

Question 2

path of galactose from intestines to hepatocytes

Answer 2

intestinal lumen —SGLT1—> enterocytes —GLUT2—> hepatic portal vein —GLUT2—> hepatocyte

Question 3

what happens to fructose after entering the liver

Answer 3

converted to fructose 1 phosphate by fructokinase

reqs 1 ATP

Question 4

what happens to galactose after entering the liver

Answer 4

converted to galactose 1-phosphate, requires 1 ATP

galactokinase

Question 5

two fructose metabolism disorders

Answer 5

essential fructosuria (benign)
hereditary fructose intolerance (severe)

Question 6

essential fructosuria

Answer 6

AR mutation in fructokinase, accumulation of fructose, benign, peed out

Question 7

herediatary fructose intolerance

Answer 7

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

Question 8

two galactose metabolism disorders

Answer 8

classical galactosemia (severe) 
nonclassical galactosemia (not severe)

Question 9

classical galactosemia

Answer 9

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

Question 10

nonclassical galactosemia

Answer 10

AR deficiency in galactokinase, buildup of galactose in blood and tissues, galactitol can accumulate in lens –> cataracts, not as severe as classical

Question 11

what does sorbitol dehydrogenase do

Answer 11

converts sorbitol to d-fructose

Question 12

what happens to excess glucose

Answer 12

converted to fructose, with sorbitol as intermediate

Question 13

what happens when you have increased levels of sorbitol

Answer 13

some tissues have relatively lower amounts of sorbitol dehydrogenase, sorbitol buildup fucks up osmotic balance, cell damage

linked to diabetic retinopathy, cataracts, peripheral neuropathy

Question 14

other names for pentose phosphate pathway

Answer 14

hexose monophosphate shunt

phosphogluconate pathway

Question 15

pentose phosphate pathway 2 main points

Answer 15

1) generates NADPH for rxns requiring reducing equivalents

2) generates ribose 5-phosphate for nucleotide biosynthesis

Question 16

two stages of pentose phosphate pathway

Answer 16

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)

Question 17

G6P dehydrogenase deficiency

Answer 17

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

Question 18

normal fxn of G6P dehydrogenase

Answer 18

the NADPH produced SHOULD control levels of reduced glutathione in cell, reduced glutathione is responsible for controlling oxidative stress in cells.