glycogen Flashcards
How does glucugon regulate glycogen levels?
glucugon binds glucugon receptor in liver. this activates adenylate cyclase. adenylate cyclase converts ATP to cAMP. cAMP activates protein kinase A. protein kinase A activates glycogen phosphorylase kinase, which activates glycogen phosphorylase. glycogen is converted to glucose (try drawing). PKA also inhibits glycogen synthetase
How does epinephrine regulate glycogen in BOTH liver and muscle? (common pathway)
epinephrine binds the beta receptor. adenylate cyclase is activaed. converts ATP to cAMP. cAMP activates protein kinase A. PKA activates glycogen phosphorylase kinase. glycogen phosphorylase kinase activates glycogen phosphorylase, which converts glycogen to glucose. PKA also inhibits glycogen synthase.
How does epinphephrine regulate glycogen in liver alone?
epi binds alpha receptors in liver. this activates the endoplasmic reticulum to release calcium. calcium activates glycogen phosphorylase kinase. glycogen phosphorylase kinase activates glycogen phosphorylase. glycogen made to glucose
How does insulin regulate glycogen?
in liver and muscle, insulin binds a tyrosine kinase dimer. this activates gycogen synthase directly. it also activates protein phosphorylase, an enzyme that inhibits glycogen phosphorylase.
glycogen structure
branches have alpha 1,6 bonds. linkages have alpha 1,4 bonds.
What happens to glycogen in muscle?
undergoes glycogenolysis to glucose-1-P. this is converted to glucose-6-P, which is metabolized.
What happens to glycogen in hepatocytes?
it is stored. it can undergo glycogenolysis to help maintain blood sugar.
Von Gierke disease: manifestations and cause
aka glycogen storage disease type 1. causes severe fasting hypoglycemia, incr. glycogen in the liver, incr. blood lactate, and hepatomegaly. d/t a deficiency in glucose-6-phosphatase (glucose-6-P can’t turn to glucose in liver, so liver can’t supply body during fasts).
Von Gierke disease tx
frequent oral glucose/cornstarch; avoidance of fructose and galactose
Pompe disease: findings, deficiency
cardiomyopathy and systemic findings leading to early death.
due to a problem with lysosomal alpha-1,4 glucosidase (acid maltase). hurst the heart, liver, and muscle.
(type II)
Cori disease: findings, deficiency
milder form of type I (von gierke disease) that has normal blood lactate levels (but may still have fasting hypoglycemia, hepatomegaly, glycogen in liver. this is due to a defect in debranching enzyme. gluconeogenesis is intact. AR disease. give oral glucose.
McArdle disease findings
type V. incr. glyogen in muscle but can’t break it down. causes painful muscle cramps, myoglobinuira (red urine) with strenuous exercise, and arrhythmia from electrolyte abnormalities.
What is the deficiency in McArdle disease?
skeletal muscle glycogen phosphorylase
