Glycogen Metabolism

Question 0

Blood glucose sources

Answer 0

Dietary free glucose: 3 hours, fed

Liver glycogen 4-16 hours, fasting

Gluconeogenesis: starts well before all liver glycogen is gone, fasting

Question 1

Glycogen

Answer 1

Stores glucose as glycogen in the fed state (liver and muscle)
Liver glycogen helps maintain blood glucose levels during fasting state
Must have glucose for: rbcs, brain, exercising muscle

Question 2

Muscle glycogen

Answer 2

Just for muscular activity
On demand
Epinephrine
Maximal energy sources for muscle contraction

Question 3

Glycogen structure

Answer 3

Branched chain glucose polymer
Alpha 1–>4 links in chains
Alpha 1–>6 links at branches
Large molecule

Question 4

Glycogen synthesis and breakdown

Answer 4

Glycogenesis: glucose units added to the ends of each chain. Adds a UDP to make it activated

Glycogenolysis: cutting glucose units off glycogen. No ATP needed, make glucose-p

Hormonal control:

Insulin, fed state: turns on glycogen synthesis, turns off breakdown. Muscle and live

Glucagon, fasting state: turns on glycogen breakdown, turns off synthesis (liver)

Epinephrine (excited state): turns on glycogen breakdown, turns off synthesis (muscle and liver)

Glucagon and epinephrine activate kinase cascade
Insulin activates protein phosphatases

Question 5

Liver vs. muscle glycogen

Answer 5

Inactivated glycogen synthesis using glucagon and epinephrine in the liver

Only use epinephrine to inactive glycogen synthesis in muscled

Insulin activate protein phosphatase, reverse feats pf glucagon. Synthesis of glycogen is on

Question 6

Glycogen storage disorders

Answer 6

An underlying genetic mutations results in accumulation of glycogen

Van Gierkes disease: defect in glucose-6-phosphatase

McArdles disease: defect in muscle glycogen phosphorylase

Hers disease: defect in liver glycogen phosphorylase