Glycogen breakdown and gluconeogenesis

Question 1

how long do dietary carbs last?

Answer 1

3-4 hours

Question 2

how long does glycogen last?

Answer 2

30 hours

Question 3

where is gluconeogenesis done?

Answer 3

liver

Question 4

where does energy between meals come from?

Answer 4

adipose triglycerides

muscle proteins if absolutely necessary

Question 5

where is glycogen broken down?

Answer 5

liver and skeletal muscle

Question 6

what does liver glycogen phophorylase do?

Answer 6

cleaves alpha 1,4 linkages by phophoryolysis, releasing 1 G-1-P at a time

Question 7

what does debranching enzyme do?

Answer 7

rearranges the branch so that 1 glucose is left and then cleaves the alpha 1,6 link via hydrolysis, releasing free glucose

Question 8

how much G-1-P is released? free glucose?

Answer 8

G-1-P 92%

free glucose 8%

Question 9

what is the difference between liver and muscle glycogenolysis?

Answer 9

liver has glucose-6-phosphatase which cleaves G-6-P to free glucose which is released into the blood
liver does not

Question 10

what does glucose-6-phosphatase do?

Answer 10

cleaves glucose-6-phosphate to free glucose

Question 11

what is phosphoglucomutase?

Answer 11

isomerizes glucose-1-P to glucose-6-P

Question 12

what is gluconeogenesis?

Answer 12

making glucose

Question 13

what are the 3 irreversible steps of glycolysis that have to be bypassed during gluconeogenesis? what do they do?

Answer 13

hexokinase- changes free glucose to glucose-6-phosphate
phophofructokinase- phophorylates fructose-6-phosphate
pyruvate kinase- changes PEP to pyruvate, releasing ATP

Question 14

how are the 3 irreversible steps of glycolysis bypassed?

Answer 14

pyruvate carboxylase
PEP carboxylase
fructose-1,6-bisphophatase
liver glucose-6-phosphatase

Question 15

what are the 4 requirements for gluconeogenesis? where do they come from?

Answer 15

NADH
energy
Acetyl CoA
Carbons
everything except carbons comes from fatty acid oxidation

Question 16

what is the energy cost of gluconeogenesis?

Answer 16

4 ATP

2 GTP

Question 17

can carbons from acetyl CoA be used in gluconeogenesis?

Answer 17

No- pyruvate dehydrogenase is not reversible

Question 18

how can fatty acids be used to make glucose?

Answer 18

odd chains are broken down into propinyl-CoA, a 3 carbon compound that can be converted to succinyl-C-A (TCA cycle intermediate, which can form oxaloacetate via TCA cycle

Question 19

what is DHAP? where can it come from? what is it used for?

Answer 19

dihydroxyacetone phophate
made from glycerol, fructose
used as a carbon substrate for gluconeogenesis

Question 20

what happens in glycogen storage diseases?

Answer 20

glycogen can’t be broken down so it accumulates in cells

due to issues in glycogen breakdown, gluconeogenesis, or fatty acid oxidation

Question 21

what is Von Gierke’s disease?

Answer 21

deficiency in liver glucose-6-phosphatase- can’t change G6P to free glucose
symptoms- severe hypoglycemia due to lack of glycogenolysis and gluconeogenesis
cannot be helped by galactose or fructose

Question 22

what are the 3 glycogen storage diseases

Answer 22

Von Gierke’s
Hers Disease
McArdles

Question 23

what is Hers Disease?

Answer 23

deficiency in liver glycogen phosphorylase
symptoms- milder hypoglycemia (gluconeogenesis works)
can be treated with fructose or galactose

Question 24

what is McArdle’s Disease?

Answer 24

deficiency in muscle glycogen phophorylase

symptoms: none, only muscle glycogen can’t be used