Metabolism 3

Question 1

Essential Fructosuria

• Enzyme deficiency
• Sx
• Mech
• Tx

Answer 1

• fructokinase
• asymptomatic
• fructose never enters cells. only in blood and urine
• none

Question 2

Fructose intolerance

• enzyme deficiency
• Sx
• Mech

Answer 2

• aldolase B
• hypoglycemia, jaundice, cirrhosis, vomiting
• F-1-P accumulates, depleting Pi, and inhibiting glycogenolysis and gluconeogenesis
• reduce intake of sucrose and fructose

Question 3

An infant fails to track objects with eyes and fails to develop a social smile. Galactose is found in the urine. What is the problem?

Answer 3

Galactokinase deficiency - causes infantile cataracts.

Question 4

A poorly controlled diabetic pt. develops cataracts, retinopathy, and peripheral neuropathy. What sugar is responsible for this damage? How? What enzyme do Schwann cells, lens, retina, and kidneys lack that permits this sort of damage?

Answer 4

Sorbitol is not converted to fructose b/c these cells lack sorbitol d.h. Accumulated sorbitol causes ozmotic damage.

Question 5

What enzyme converts glucose to sorbitol?

Answer 5

Aldose reductase, available in some tissues.

Question 6

Explain ethanol hypoglycemia.

Answer 6

EtOH metabolism increases NADH/NAD+ ratio, diverting pyruvate to lactate and OAA to malate. Gluconeogenesis is inhibited and and FA synthesis is stimulated. Inhibition of TCA cycle shunts ACoA to ketone production.