Glycogen breakdown and gluconeogenesis Flashcards
how long do dietary carbs last?
3-4 hours
how long does glycogen last?
30 hours
where is gluconeogenesis done?
liver
where does energy between meals come from?
adipose triglycerides
muscle proteins if absolutely necessary
where is glycogen broken down?
liver and skeletal muscle
what does liver glycogen phophorylase do?
cleaves alpha 1,4 linkages by phophoryolysis, releasing 1 G-1-P at a time
what does debranching enzyme do?
rearranges the branch so that 1 glucose is left and then cleaves the alpha 1,6 link via hydrolysis, releasing free glucose
how much G-1-P is released? free glucose?
G-1-P 92%
free glucose 8%
what is the difference between liver and muscle glycogenolysis?
liver has glucose-6-phosphatase which cleaves G-6-P to free glucose which is released into the blood
liver does not
what does glucose-6-phosphatase do?
cleaves glucose-6-phosphate to free glucose
what is phosphoglucomutase?
isomerizes glucose-1-P to glucose-6-P
what is gluconeogenesis?
making glucose
what are the 3 irreversible steps of glycolysis that have to be bypassed during gluconeogenesis? what do they do?
hexokinase- changes free glucose to glucose-6-phosphate
phophofructokinase- phophorylates fructose-6-phosphate
pyruvate kinase- changes PEP to pyruvate, releasing ATP
how are the 3 irreversible steps of glycolysis bypassed?
pyruvate carboxylase
PEP carboxylase
fructose-1,6-bisphophatase
liver glucose-6-phosphatase
what are the 4 requirements for gluconeogenesis? where do they come from?
NADH energy Acetyl CoA Carbons everything except carbons comes from fatty acid oxidation
what is the energy cost of gluconeogenesis?
4 ATP
2 GTP
can carbons from acetyl CoA be used in gluconeogenesis?
No- pyruvate dehydrogenase is not reversible
how can fatty acids be used to make glucose?
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
what is DHAP? where can it come from? what is it used for?
dihydroxyacetone phophate
made from glycerol, fructose
used as a carbon substrate for gluconeogenesis
what happens in glycogen storage diseases?
glycogen can’t be broken down so it accumulates in cells
due to issues in glycogen breakdown, gluconeogenesis, or fatty acid oxidation
what is Von Gierke’s disease?
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
what are the 3 glycogen storage diseases
Von Gierke’s
Hers Disease
McArdles
what is Hers Disease?
deficiency in liver glycogen phosphorylase
symptoms- milder hypoglycemia (gluconeogenesis works)
can be treated with fructose or galactose
what is McArdle’s Disease?
deficiency in muscle glycogen phophorylase
symptoms: none, only muscle glycogen can’t be used
