Biochem Fructose And Galactose Metabolism

Front 1

first thing that happens to fructose

and the enzyme that does it

Back 1

gets phosphorylated to Fructose 1-phosphate

by Fructokinase

Front 2

metabolism of Fructose 1-P

Back 2

Aldolase B converts Fructose 1-P to


dihydroxyacetone phosphate (DHAP)

and

glyceraldehyde

Front 3

what happens to the glyceraldehyde and DHAP evolved in the metabolism of Fructose

Back 3

the DHAP launches into the glycolytic cycle

the glyceraldehyde is phosphorylated by Triose kinase

and follows on

Front 4

why is fructose metabolized faster than glucose

Back 4

its products enter the glycolytic cycle after PFK1, the major regulatory step

Front 5

hereditary fructose intolerance is a defect in the gene

Back 5

Aldolase B


no symptoms unless fructose is ingested

hypoglycemia

Front 6

essential fructosuria

a deficiency in the enzyme __________

Back 6

fructokinase

fructosuria

usu. benign- fructose in urine

Front 7

many tissues can create fructose from glucose via the intermediate __________

Back 7

sorbitol

thats where the sorbitol in cataracts comes from

they call it the Polyol pathway

Front 8

in Hereditary Fructose Intolerance

how can eating fructose cause a hypoglycemic event?

Back 8

defect in Aldolase B causes an accumulation of Fructose 1-phosphate

Fructose 1-P stimulates glycolysis via a feed-forward effect on pyruvate kinase

while simultaneously inhibiting glycogen phosphorylase

and tying up all the phosphate so there's not enough to drive gluconeogenesis

Front 9

what is the main source of galactose in the diet

Back 9

from lactose

Front 10

first step in the metabolism of galactose, and the enzyme

Back 10

phosphorylation to galactose 1-phosphate

by the enzyme galactokinase

Front 11

in galactose metabolism, what does Galactose 1-P react with

and what is the product of the reaction

Back 11

UDP-glucose

via the enzyme galactose 1-phosphate uridyl transferase


the product of the reaction is Glucose 1-phosphate, which can be converted to Glc 6-P by phosphoglucomutase

Front 12

in galactose metabolism

what becomes of the UDP-galactose formed in the transformation of Galactose 1-P to Glucose 1-P

Back 12

the UDP-galactose is converted to UDP-glucose again by an enzyme called

4-epimerase

Front 13

what can result from Galactokinase deficiency

Back 13

galactosemia

galactosuria

galacticol, the sugar alcohol, can accumulate in the lens of they eye, causing cataracts

Front 14

classical galactosemia is a deficiency of what enzyme

Back 14

galactose 1-phosphate uridyl transferase

Front 15

deficiency of galactose 1-phosphate uridyl transferase can lead to

Back 15

galactosemia, galactosuria and cataracts

AND liver damage and mental retardation as Gal 1-P accumulates and ties up all the organic phosphate

Front 16

in lactose synthesis, what form is the galactose used

Back 16

UDP-galactose

Front 17

lactose synthase has two subunits

one is galactosyl transferase

one of them isn't even an enzyme but a modifier protein. What is its name and why is it interesting

Back 17

alpha-lactalbumin

it is synthesized after childbirth in response to prolactin

alpha-lactalbumin combines with galactosyl transferase and lowers its Km for glucose from 1200 mM to 1 mM