Enzymes
What is the key regulatory enzyme in the degradation of glycogen?
Glycogen phosphorylase
What is the main function of the liver that has to do with glycogen?
Maintain blood-glucose levels
What is the main function of the muscle that has to do with glycogen?
Muscle contraction
Adenylate cyclase catalyzes the formation of what second messenger?
cAMP
What is glycogen?
A branched polymer of glucose residues
DOUBLE JEOPARDY!
What are the two forms that phosphorylase can exist in?
What state does each form favor?
less active b form, more active a form
b favors the Tstate and a favors the Rstate
What is the default form of phosphorylase in the liver?
Phosphorylase a
What is the default form of phosphorylase in muscle?
Phosphorylase b
How do protein kinase and glycogen synthase kinase work together?
They add a phosphoryl group to glycogen synthase that leads to a decrease in its activity
What role does glycogenin play?
Serves as a primer for glycogen synthase
DOUBLE JEOPARDY!
What is the key regulatory enzyme in glycogen synthesis?
What kind of linkages can this enzyme form?
Glycogen synthase
alpha-1,4-linkages
DOUBLE JEOPARDY!
What hormone(s) bind to breakdown or synthesize glycogen in the liver?
What would cause this to be in higher amounts in the body?
Insulin triggers synthesis, Glucagon triggers breakdown
Low blood-glucose levels
DOUBLE JEOPARDY!
What hormone(s) bind to breakdown or synthesize glycogen in the liver?
What would cause this to be in higher amounts in the body?
Epinephrine (adrenaline)
Fear or excitement of exercise
How is phosphorylase b converted into phosphorylase a?
Phosphorylation of serine 14 in each subunit
Why is Hers disease considered more "deadly" than McArdle disease?
Hers disease affects the liver and the liver is responsible for contributing to the body's homeostasis.
McArdle disease affects muscle and therefore only affects muscle contraction.
What does UDP-glucose pyrophosphorylase do?
Catalyzes the reaction between glucose 1-phosphate and UTP to form UDP-glucose
What inhibits liver phosphorylase a?
Glucose
What type of muscle fiber is indicated by the following:
Type I:
Type IIa:
Type IIb:
Type I: slow-twitch
Type IIa: intermediate
Type IIb: fast-twitch
What is the job of PP1 in stopping the breakdown of glycogen?
Removes the phosphoryl groups from phosphorylase kinase and glycogen phosphorylase to inactivate them
Why is branching necessary?
It increases the rate of both glycogen synthesis and glycogen degradation
What is the difference between a phosphorylase and a phosphatase?
A phosphorylase catalyzes the reaction of ADDING a phosphate group.
A phosphatase catalyzes the reaction of REMOVING a phosphate group.
What enzyme does the liver have (that the muscle does not) that enables glucose to leave the organ?
Glucose 6-phosphatase
What activates muscle phosphorylase?
High concentrations of AMP
What are the two reasons that the conversion of glucose 1-phosphate into glucose 6-phosphate is a favorable reaction?
1) the released sugar is already phosphorylated
2)there are no transporters for glucose 1-phosphate in muscle cells
Insulin can facilitate glycogen synthesis by increasing:
By increasing the number of glucose transporters (GLUT4)