Flashcards in 2.1 Fructose metabolism Deck (44)
Key sources of fructose in diet
High Fructose Corn Syrup
What are the two monosaccharides that make up Sucrose
Glucose and Fructose
What is the key difference between High Fructose Corn Syrup and Sucrose
Sucrose is a disaccharide of Glucose and Fructose
HFCS is a mixture of monosaccharides of Glucose and Fructose
Fructose absorption into the intestinal cells occurs how and through what type of transport?
Through GLUT 5
Fructose absorption into the bloodstream from the intestinal cells occurs how and through what type of transport?
GLUT 5 or GLUT 2 (mainly GLUT 2)
In the muscle, how in what structure does fructose enter glycolysis
Fructose --> Fructose 6-phosphate
What enzyme catalyzes the reaction of Fructose to Fructose 6-phosphate in the muscle?
How does Fructose enter glycolysis in the liver
Fructose --> Fructose 1-phosphate --> Glyceraldehyde and Dihydroxyacetone phosphate --> Glyceraldehyde 3-phosphate
What enzyme catalyzes reaction of fructose to fructose 1-phosphate in the liver
What enzyme catalyzes Fructose 1-phosphate to Glyceraldehyde and Dihydroxyacetone phosphate
Aldolase B (Fructose 1-phosphate aldolase)
What crucial step of normal glycolysis does Fructose skip as it enters glycolysis in the liver?
It bypasses PFK1
What is the result of Fructose bypassing PFK1 in the liver?
Increased lipogenesis and Increased appetite
Excessive dietary intake of fructose may lead to decrease in what?
available phosphate which means that it is insufficient to meet demands of ATP regeneration
What are the two major genetic disorders of fructose metabolism
Enzyme deficiency with Fructokinase
Enzyme deficiency with Aldolase B
Which genetic disorder of fructose metabolism is severe
Enzyme deficiency with Aldolase B or Hereditary fructose intolerance
What happens when there is an enzyme deficiency with fructokinase in the liver?
Fructose cannot be phosphorylated to fructose 1-phosphate and cannot be trapped in the cell. This could lead to Essential Fructosuria
What is the purpose of converting glucose to sorbitol?
To trap glucose in the cell without expending ATP.
What enzyme catalyzes the reaction of Glucose to Sorbitol?
What coenzyme is used in the reaction of Glucose to Sorbitol?
When is there a buildup of Sorbitol?
In what cells does Sorbitol build up and why?
Lens, Kidney and Nerve
Sorbitol cannot be converted to Fructose in these cells
Sorbitol is converted to Fructose by what enzyme in the Liver?
How does Mannose enter glycolysis?
By being converted to Fructose 6-phosphate
Reaction of Mannose to Mannose 6-phosphate is catalyzed by what enzyme?
Mannose 6-phosphate to Fructose 6-phosphate reaction is catalyzed by what enzyme?
How does Galactose enter glycolysis?
Briefly outline the pathway of Galactose being converted to Glucose 6-phosphate
*Galactose --> Galactose 1-phosphate
*Galactose 1-phosphate + UDP-Glucose --> UDP-Gal + Glu 1-Phosphate
*Glucose 1-phosphate --> Glucose 6-phosphate
**UDP-galactose --> UDP-glucose (to be used to produce glu-1-P)
What enzyme catalyzes the reaction of Galactose --> Galactose 1-phosphate
What enzyme catalyzes the placement of uridine phosphate on Galactose 1-phosphate and the production of Glucose-1-phosphate
Galactose 1-phosphate uridylyl transferase