Carbohydrate Metabolism II

Question 1

Major non-carb precursors for gluconeogensis

Answer 1

amino acids (mainly alanine), lactate, glycerol

Question 2

Main regulated step of gluconeogensis

Answer 2

Fructose 1,6 bisphosphate to fructuose 6-phosphate by fructuse 1,6 phosphatase

Question 3

Fructose 2,6 bisphosphate

Answer 3

made by phosphofructosekinase II from fructose-6-phosphate.

Question 4

Role of fructose 2,6 bisphophate in gluconeogensis

Answer 4

inhibits fructose 1,6 bisphosphatase

Question 5

Role of fructose 2,6 bisphosphate in glycolysis

Answer 5

stimulates phosphofructokinase I

Question 6

Lactose synthesis

Answer 6

Made in mammary gland from glucose and galatose
Synthensis starts from UDP-glucose, which is epimerized to UDP-galactose before lactose synthase condenses it with glucose

Question 7

Purpose of PPP

Answer 7

To generate NADPH and to rearrange carbons to creates pentoses, hexoses, trioses, needed to connect with glycolysis and gluconeogeneis

Question 8

Main regulated/committed step of PPP

Answer 8

G6P to phosphoglucolactone by glucose 6-phosphate dehydrogenase. Inhibited by NADPH

Question 9

Cell needs NADPH and ribose at the same time

Answer 9

make both using G6P

Question 10

Cell is full of NADPH but needs ribose

Answer 10

High NADPH shuts down oxidative phase of PPP, so use non-oxidative phase to rearrange carbons and produce ribose

Question 11

Cell has enough ATP and ribose, but needs NADPH

Answer 11

Send glucose to PPP to make NADPH. Extra ribose that builds up is rearranged in non-oxidative phase to F6P and CAP and sent to gluconeogensis to make glucose

Question 12

Growing cell that has enough ribose, but needs ATP and NAPDH

Answer 12

glucose goes through PPP oxidative phase to make NADPH.

Extra ribose made is rearranged in non-oxidative phase into pyruvate and sent to glycoysis to make ATP

Question 13

Clinical presentation of gluconeogensis defects

Answer 13

will cause a buildup of precursors of glucose , hypoglycemia, and metabolic acidosis

Question 14

Glucose-6-p dehydrogenase deficieny

Answer 14

reduces PPP activity. Cells won’t have enough NADPH. Impairs reduction pathways, and deprives rbcs from anti-oxidant protection because they become sensitive to increased levels of H2O2

Question 15

Beri Beri

Answer 15

thiamin requires in non-oxidative phase of the PPP pathway, which is only NADPH source for RBCs. Deficiency ruins rbcs