Pentose Phosphate Pathway, Fructose And Galactose Metabolism

Front 1

What are the functions of the pentose phosphate cycle?

Back 1

Generates NADPH for production of fatty acid synthesis and glutatione reduction.
Generates ribose-5-phosphate for nucleotide biosynthesis.

Front 2

How is fructose added into the glucose pathway?

Back 2

Fructose converted to fructose-1-P by fructokinase.
Fructose-1-P converted to glyceraldehyde and dihydroxyacetone-P by aldolase B.
Glyceraldehyde converted to glyceraldehyde-3-P by triose kinase.
Glyceraldehyde-3-P and dihydroxyacetone-P can be used in the glycolysis cycle.

Front 3

What deficiency is associated with hereditary fructose intolerance? What are the symptoms?

Back 3

Aldolase B defect, leads to intracellular trapping of fructose-1-P.
Leads to severe hypoglycemia, vomiting, jaundice, hemorrhage, hepatomegaly, hyperuricemia, hepatic failure, death.

Front 4

What deficiency occurs with essential fructosuria? What are the results?

Back 4

Lack of fructokinase.
Benign condition.
Fructose accumulates in the urine.

Front 5

How is fructose synthesized through sorbitol? Which tissues undergo this process?

Back 5

Glucose converted to sorbitol by aldose reductase.
Sorbitol converted to fructose by sorbitol dehydrogenase.
Aldose reductase found in lens, retina, Shwann cells, liver, kidney, ovaries, and seminal vesicles.
Sorbitol dehydrogenase found in sperm and liver.

Front 6

When does polyol production occur? When does it cause a problem?

Back 6

In conditions of hyperglycemia, sugars diffuse into tissues. Converted to polyols by aldose reductase, but tissues have no sorbitol dehydrogenase, causing buildup of sorbitol.
Results in cataracts, peripheral neuropathy, vascular problems- diabetic

Front 7

How is galactose converted to a glycolysis intermediate?

Back 7

Galactose converted to galactose-1-P by galactokinase.
Galactose-1-P converted to glucose-1-P by galactose-1-P urilyltransferase with UDP-glucose.

Front 8

What causes nonclassical galactosemia? What causes classical galactosemia?

Back 8

Nonclassical-buildup of galactose due to galactokinase deficiency.
Classical-buildup of gal-1-P due to galactose-1-P uridylyltransferase deficiency.

Front 9

What are symptoms of classical galactosemia?

Back 9

Cataracts in neonates
Vomiting, diarrhea, jaundice
Liver damage
Mental retardation
No hypoglycemia occurs

Front 10

What are the effects of G6PDH? Why?

Back 10

Oxidant drugs, fava beans, or infection result in hemolytic anemia.
Deficiency in the enzyme that initiates the pentose phosphate pathway. NADPH is not produced, and glutathione is not reduced.

Front 11

How does NADPH prevent oxidative damage? What occurs when this cycle is interrupted?

Back 11

NADPH reduces oxidized glutatione, which converts H2O2 to 2 water molecules. Without the NADPH, ROS produce hemolysis and the oxidezed glutathione produce heinz bodies.