Glycogenesis & Glycogenolysis Flashcards
1
Q
Glycogen
A
- polymeric form in which glucose is stored
- granules found in cytoplasm of cells
- granules have protein in center called glycogenin that connects 100s of glucose molecules in chain form
2
Q
Glycogenesis
A
- formation of glycogen
- occurs when there is high levels of blood glucose
- stimulated by insulin
- glucose monomers get converted into glycogen polymer
- stored mainly in liver, and to a lesser extent in skeletal muscle
3
Q
Glycogen Synthase
A
- rate-limiting enzyme in glycogenesis
- forms the alpha-1,4-glycosidic bond found in linear chains of glucose in the granule
- inhibited by epinephrine, glucagon, and AMP
- stimulated by insulin and ATP
4
Q
Branching Enzyme
A
- used in glycogenesis
- takes a linear chain and introduces branch points by breaking (hydrolyzing) alpha-1,4-glycosidic bonds and reforming alpha-1,6-glycosidic link
- the more branches the greater efficiency that energy can be stored
5
Q
Glycogenolysis
A
- breakdown of glycogen
- occurs when there are low levels of blood glucose
- stimulated by glucagon, epinephrine, and AMP
- glycogen polymer gets converted into glucose monomers
6
Q
Glycogen Phosphorylase
A
- rate limiting enzyme in glycogenolysis
- phosphorylates peripheral alpha-1,4-glycosidic bonds which releases glucose 1-phosphate
- stops at branch points because unable to break alpha-1,6-glycosidic bonds
- inhibited by insulin and ATP
- stimulated by epinephrine, glucagon, and AMP
7
Q
Debranching Enzyme
A
- used in glycogenolysis
- two-enzyme complex that deconstructs the branches in glycogen that have been exposed by glycogen phosphorylase
8
Q
List the 3 steps of the debranching enzyme
A
- breaks alpha-1,4-glycosidic bond of the branch point and moves the released oligoglucose chain to the exposed end of another chain
- forms a new alpha-1,4-glycosidic bond
- glucosidase hydrolyzes alpha-1,6-glycosidic bond which releases a single glucose from the branch
