what is the storage form of glucose?
glycogen
what are the primary storage sites for glycogen?
liver and skeletal muscle
what is a polymer?
many glucose molecules bound together
glycosidic chains of glucose are connected by?
a (1-4) bonds
glycosidic branch points of glucose are connected by?
a(1-6) bonds
glycogen branching occurs every?
10 glucose molecues
-provides increased solubility and easier access to glucose
where is glycogen found?
cytosol or cytoplasm
what are some reasons why we would need to begin glycogen degradation or breakdown?
diet is insufficient
increased demand for ATP
gluconeogenesis is slow
when exercising, glycogen in muscle can break down and release what?
glucose-6-phosphate
what enzyme do we need to break a(1-4) bonds?
glycogen phosphorylase
what coenzyme does glycogen phosphorylase need to break the a(1-4) bond?
pyridoxal phosphate
what is the product when we break the a(1-4) bond?
glucose-1-phosphate
what is glucose-1-phosphate converted into glucose-6-phosphate by?
phosphoglucomutase- I think we just need to know its a mutase
what pathway uses glucose-6-phosphate?
glycolysis
once glucose is trapped in a muscle it is not available for other tissues, why?
lacks the enzyme needed to release glucose
glucose-6-phosphate is converted into?
free glucose where it is sent to the cytosol and released into the blood stream
what type of bond can glycogen phosphorylase not break?
a(1-6) bonds
glycogen breakdown continues until?
we are 4 glucose residues away from the branch
what are the 2 enzymes required to cut the glucose branches?
glucosyl (4:4) transferase
amylo-a (1-6) glucosidase
both a(1-6) enzymes
what is the key regulatory enzyme of glycogenolysis?
glycogen phosphorylase
what hormones attach to the cell membrane and activate adenylyl cyclase to produce cAMP?
glucagon
epinephrine
norepinephrine
where is adenylyl cyclase located?
plasma membrane- catalyzes reaction resulting in cyclic AMP
cAMP stimulates which powerful enzyme?
AMP kinase, PKA, protein kinase A
glycogen phosphorylase B is active or inactive?
inactive
AMP binds to glycogen phosphorylase A or B?
B
AMP binding to glycogen phosphorylase B does what to glycogen synthesis?
inhibits it
what binds to glycogen phosphorylase A and what does it do to it?
ATP binds to it and inhibits it
when calcium binds to calmodulin to form the CaCaM complex what gets activated?
glycogen phosphorylase kinase
what releases calcium in the muscle?
neural stimulation
what releases calcium in the liver?
epinephrine
calmodulin is a subunit of what?
glycogen phosphorylase kinase
neural stimulation releases calcium from where?
sarcoplasmic reticulum and binds to calmodulin
where is epinephrine released from and what does it need to release?
adrenal medulla and it needs glucose
the liver releases Ca from what and sends it where?
it releases it from the ER and sends it to the cytoplasm
where do you find glycogen in the brain?
astrocytes
embryonic neurons
where is the highest concentration of glycogen in the brain?
where there is increased synaptic activity
2x more in gray matter than white matter
what is essential for glutamate neurotransmission?
glycogen
what stimulates glycogenolysis?
low energy- increased ADP AMP epinephrine/ norepinephrine glucagon calcium- muscle contraction, stress response AMP kinase
what stimulates glycogenesis?
increased ATP
increased insulin or glucose
what are the enzymes we need to know for glycogenolysis?
glycogen phosphorylase phosphoglucomutase glucosyl- (4:4)- transferase amylo-a-(1-6)- glucosidase glucose-6- phosphatase
final reminder, where is glycogenolysis located?
cytosol