biochem- glycogenesis and glycogenolysis

provide animals with a ready supply of glucose to supply the brain and skeletal muscles with energy

what is the function of glycogen?

skeletal muscles, brain

glycogen is a form of stored glucose that has the purpose of providing __________ with energy (what parts of the body?)

fat- but fat cannot be degraded into glucose

the most common form of stored energy is....

polymeric

glucose is stored in a _____ form called glycogen

liver and skeletal muscles

glycogen is stored where in the body?

provides glucose needed for muscle contraction within seconds

what is the purpose of glycogen that is stored in the skeletal muscles?

provides a reservoir for maintaining blood glucose levels

what is the purpose of glycogen that is stored in the liver?

glycogenin

what is the primer needed for the synthesis of glycogen called?

a1-4; a1-6

within glycogen, each glucose is attached with a ______ bond, and each branch is attached with a _______ bond

the non-reducing end

the fourth carbon of glycogen is free, and it is called _______

glycogenesis

the metabolic process that synthesizes glycogen is called ________

glycogenolysis

the breakdown of glycogen is called________.

breakdown of glycogen into glucose 1-phosphate

glycogenolysis is the __________

glucose 1-phosphate

when glycogen is broken down, it forms ________

a protein primer and an activated glucose precursor (glycogenin)

what are the 2 components needed to begin glycogenesis?

sugar nucleotides; non-reducing end of the growing linear chains in the outer tiers of the glycogen beta molecules

in glycogenesis, individual glucose molecules activated as ______ are added to the _______

to the nonreducing end of the chains in the outer tiers of the glycogen beta molecules

in glycogenesis, where are the individual activated glucose molecules added ?

the activation of glucose. this is done by UDP glucose pyrophosphorylase, which converts glucose 1-phosphate to UDP glucose (a sugar nucleotide)

what is the very first step of glycogenesis?

UDP glucose.

UDP glucose pyrophosphorylase

in the first step of glycogenesis, glucose 1-phosphate is converted into _______ by what enzyme?

glycogen synthase catalyzes the transfer of the glucose residue from UDP glucose to a nonreducing end of a branched glycogen molecule, forming an a1-4 bond

after activated into UDP glucose, what is the next step of glycogenesis?

glycogen synthase

what enzyme catalyzes the transfer of the glucose residue from UDP-glucose to a nonreducing end of a branched glycogen molecule?

it transfers the glucose residue from UDP-glucose to a nonreducing end of a branched glycogen molecule, forming a a1-4 bond

what does glycogen synthase do? to what metabolic process does it belong?

glycogen branching enzyme

what enzyme catalyses the formation of a1-6 bonds?

catalyzes the formation of a1-6 bonds found at the branch points of glycogen

what does glycogen branching enzyme do?

protein phosphorylase 1 (PP1)

what molecule activates glycogen synthase?

glycogen synthase a; glycogen synthase b

glycogen synthase b has phosphate groups

the active form of glycogen synthase is ______ and the inactive form is _______. which one has phosphate groups?

activates glycogenolysis and inactivates glycogenesis

what does phosphorylation do to glycogenesis/glycogenolysis?

inactivation

is phosphorylation associated with the activation or inactivation of glycogenesis?

it increases glycogenesis by inhibiting glycogen synthase kinase 3 (GSK3) and activating protein phosphatase 1 (PP1)

how does insulin impact glycogenesis?

activates glycogen synthase, activating glycogenesis

what does protein phosphatase 1 (PP1) do?

increases glycogenesis

what is the impact of a high concentration of glucose 6-phosphate on glycogenesis?

insulin

what hormone increases glycogenesis?

increases; PP1; GSK3

insulin ______ glycogenesis by activating _____ and inhibiting _____

adds a phosphate to glycogen synthase, inactivating it

what does glycogen synthase kinase 3 (GSK3) do?

yes

does the inactive form of glycogen synthase have phosphate groups?

it adds phosphate to glycogen synthase, inactivating it

how does GSK3 inactivate glycogenesis?

it removes a phosphate from glycogen synthase, activating it

how does protein phosphatase 1 (PP1) work?

protein phosphatase 1 (PP1)

what molecule activates glycogenesis by removing a phosphate from glycogen synthase?

glycogen synthase kinase 3 (GSK3)

what molecule inactivates glycogenesis by adding a phosphate to glycogen synthase?

insulin, glucose 6-phosphate

by activating PP1, a phosphate is removed from glycogen synthase, activating it, which activates glycogenesis

what molecules activate PP1?

inactivate

by inactivating GSK3, there is no phosphate group added to glycogen synthase, so it remains actively creating glycogen

does insulin activate or inactivate GSK3?

glucagon and epinephrine

by inhibiting PP1, glycogen synthase remains phosphorylated (inactive), so will not create glycogen

what hormones inhibit PP1?

hypoglycemia or if muscles need energy

when is glycogenolysis performed?

hypoglycemia

is glycogenolysis triggered by hyperglycemia or hypoglycemia?

a phosphorolysis reaction that creates phosphorylated glucose molecules that are released from glycogen and enter glycolysis to provide energy

what is glycogenolysis?

releases glucose molecules that enter glycolysis for bursts of energy

what is the function of glycogenolysis in the skeletal muscle?

allows free glucose to be transported out of the cell for use in the brain and other tissues when dietary glucose is not sufficient

what is the function of glycogenolysis in the liver?

it cleaves at the a1-4 bonds at the nonreducing ends of glycogen, releasing a glucose 1-phosphate

what does glycogen phosphorylase do?

glycogen phosphorylase

what enzyme cleaves the a1-4 bonds of glycogen, releasing a glucose 1-phosphate?

glycogenolysis

to what metabolic pathway does glycogen phosphorylase belong?

glucose 1-phosphate

when glycogen phosphorylase cleaves the a1-4 bonds of glycogen, what molecule is released?

it transfers branches onto main chains and releases the residue at the a1-6 branch as a free glucose

what does the debranching enzyme do?

debranching enzyme

what enzyme transfers branches onto main chains and releases the residue at the a1-6 branch as a free glucose?

catalyzes the reversible conversion of glucose 1-phosphate to glucose 6 phosphate

what does phosphoglucomutase do?

phosphoglucomutase

what enzyme converts glucose 1-phosphate to glucose 6-phosphate?

because:

in muscle, the purpose is to be used for energy, so we want to perform glycolysis, and glucose 1-phosphate cannot enter glycolysis- only glucose 6-phosphate can

in liver, the purpose is to increase blood glucose levels, and glucose 1-phosphate needs to be turned into glucose 6-phosphate, because it can be turned into glucose that can enter and circulate in the bloodstream

catalyzed by phosphoglucomutase

in glycogenolysis, glucose 1-phosphate molecules are released from glycogen when glycogen phosphatase cleaves at the a1-4 bonds. then, glucose 1-phosphate molecules need to be converted into glucose 6-phosphate- why? what enzyme catalyzes this conversion?

enters glycolysis

in skeletal muscle, glucose 6-phosphate released from glycogen does what next?

is converted to glucose by glucose 6-phosphatase, and exported to the bloodstream to replenish blood glucose levels

in the liver, glucose 6-phosphate released from glycogen does what next?

yes

does the active form of glycogen phosphorylase have phosphate groups?

a- active form

which form of glycogen phosphorylase (a or b) has phosphate groups?

glycogenolysis; glycogenesis

phosphorylation of glycogen synthase and glycogen phosphorylase activates _______ and inactivates ________

phosphorylase b kinase

which molecule activates glycogen phosphorylase?

glucagon

phosphorylase b kinase is the enzyme that activates glycogen phosphorylase- so activates glycogenolysis

in the liver, phosphorylase b kinase is triggered by which hormone?

epinephrine

phosphorylase b kinase is the enzyme that activates glycogen phosphorylase- so activates glycogenolysis

in the skeletal muscle, phosphorylase b kinase is triggered by which hormone?

hypoglycemia

glucagon is released during what conditions?

glycogenolysis; glycogenesis

phosphorylation activates _____ and inactivates ______

glycogenesis; glycogenolysis

dephosphorylation activates _____ and inactivates ______

glycogen phosphorylase

phosphorylase b kinase

which enzyme, when phosphorylated, performs glycogenolysis?

what enzyme catalyzes it's phosphorylation?

glycogen synthase

protein phosphatase 1 (PP1)

which enzyme, when dephosphorylated, performs glycogenesis?

what enzyme catalyzes it's dephosphorylation?

glycogen synthase kinase 3 (GSK3)

which enzyme catalyzes the phosphorylation of glycogen synthase?