Endocrine - Glycogenesis and Glycogenolysis Flashcards
What is the storage form of carbohydrates in animals?
Glycogen
What types of bonds does it have? Where?
Alpha 1-4 glucose
Alpha 1-6 glucose - branch points
What does phosphoglucomutase do in glycogenesis?
Converts Gluc-6-P to Glu-1-P
What is the product formed when UDP-glucose-pyrophosphorylase acts of glu-1-P and UTP? What makes this special?
UDP-glucose
Active form of glucose
What end of the pre-exisitng glycogen molecule are glucosyl residues added? By what type of linkage? By what enzyme?
Added to non-reducing end
Alpha 1-4 glycositic linkage
Glycogen synthase
How are branch points in glycogen formed?
When minimum of 11 glucosyl residues present, terminal 6-7 are removed as block and moved to interior site by branching enzyme, forming alpha 1-6 glycosidic linkage
What does glycogen phosphorylase do? What does it require? Why?
Remove glucose from non-reducing end of glycogen
Requires pyridoxal phosphate - derv. of B6
Provide energy for reaction
Why is a debranching enzyme also required (in addition to glycogen phosphorylase) in glycogenolysis?
Phosphorylase only removes until 4 glucose left
Glucan transferase moves triose from branch point to another branch and then debranching enzyme degrades alpha 1-6 linkage
What does insulin stimulate? Inhibit?
Stimulates - glycogenesis
Inhibits - glycogenolysis
What does glucagon stimulate? Inhibit?
Stimulates - glycogenolysis
Inhibits - glycogenesis
What does epinephrine stimulate? Where?
Stimulates glycogenolysis in liver and muscle
What is the active form of glycogen phosphorylase? Is it phosphorylated
Phosphorylase a – P (phosphorylated)
What is the inactive form of glycogen phosphorylase? Is it phosphorylated?
Phosphorylase b (not phosphorylated)
What inhibits phosphorylase a–P?
Glucose
ATP
What phosphorylates phosphorylase b to phosphorylase a? How is that phosphorylated
Phosphorylase kinase a
cAMP-dependent protein kinase (activated by glucagon)
