fructose and lactose intolerance, glactosemia and G-6-pi dehydrogenase deficiency

Question 1

what are the common disaccharides and what are they formed from?

Answer 1

lactose = galactose + glucose
sucrose = glucose + fructose
maltose = 2 glucose

Question 2

lactose intolerance

Answer 2

acquired deficiency of lactase

Question 3

galactosemia

Answer 3

loss of uridyl transferase enzyme => galactol accumulation

Question 4

fructose intolerance

Answer 4

loss of liver specific aldolase => fructose-1-Pi accumulation

Question 5

G6PDH deficiency (clinical presentation? what can induce it?)

Answer 5

most common enzymopathy
most G6PDH deficient individuals remain asymptomatic throughout life
most common manifestation is hemolytic anemia in adults and neonatal jaundice
hemolysis can be induced by drugs, infection, certain foods, chemical agents

Question 6

what does G6PDH do?

Answer 6

first enzyme in pentose phosphate pathway
forms NADPH from NADP+
G-6-P becomes 6-phsophogluconate

Question 7

why does NADPH deficiency cause cell damage?

Answer 7

glutathione reductase requires NADPH to regenerate reduced glutathione
reduced glutatione needed to protect red cells from oxidative damage

Question 8

what does the pentose phosphate pathway produce?

Answer 8

pentoses, ATP, NADPH

Question 9

what are the cofactors of glutathione reductase?

Answer 9

NADP+ and NAD+

Question 10

what does glutathione reductase do?

Answer 10

regenerates glutathione, which is needed to protect RBCs from hemolysis and oxidative damage

Question 11

what regulates G6PDH?

Answer 11

NADPH inhibits

Question 12

what does 6-phosphogluconate dehydrogenase do?

Answer 12

forms another NADPH from NADP+ using 6-phosphogluconate
makes ribulose-5-P
CO2 is a byproduct
part of pentose phosphate pathway

Question 13

what does the oxidative branch of the pentose phosphate pathway?

Answer 13

6C molecule is converted to a 5C molecule via oxidation and decarboxylation
makes NAPDH

Question 14

are reactions of the oxidative branch of the pentose phosphate pathway reversible?

Answer 14

no

Question 15

what are the products of breakdown of ribulose?

Answer 15

part of pentose phosphate pathway
can form both xylulose-5-P or ribose 5-P
formation of ribose-5-P does not form ATP or NADPH

Question 16

what does phosphopentose epimerase do?

Answer 16

part of pentose phosphate pathway

coverts ribulose-5-P to its diasteromer, xylulose=5=P

Question 17

what does phosphopentose isomerase do?

Answer 17

part of pentose phosphate pathway

converts ribulose-5-P to ribose-5-P

Question 18

what is energy providing molecule is formed if pentoses are converted to G-6-P?

Answer 18

NADPH is formed but not ATP

Question 19

what is NAPDH important for?

Answer 19

creates NADPH - used in anabolic pathway
important in glutathione reductase reaction - helps neutralize O radicals - esp important in RBCs
ribose needed for RNA and DNA synthesis