Bio Chem EXAM 4

10

glycogen branches every _____ residues

liver and muscle

the largest stores of glycogen are in the _____

liver

energy

brain and red blood cells

the ___ breaks down glycogen and releases glucose to the blood to provide ____ for the ____

muscle glycogen stores

are mobilized to provide energy for muscle contraction

glycogen phosphorylase

cleaves onlt alpha 1,4 glycosidic bonds

glucose 1-phosphate

in glycogen degradation, phosphorylase cleaves glycogen to release ______

glucose 6-phosphate

in the second step of glycogen degradation, glucomutase converts glucose 1-phosphate to _____

glucomutase

in glycogen degradation, ___ converts glucose 1-phosphate to glucose 6-phosphate

phosphoryl groups

glucose 1,6-bisphosphate

during glycogen degrdation, glucomutase makes glucose 6-phosphate with teh exchanging of different ____ by the formation of the intermediate, ____

glucose 6-phosphatase

liver

blood

____breaks down glucose 6-phosphate to glucose in the ____ and releases it into the ____

glucose

glucose 6-phosphate cannot move out of the cells, but ____ can

free glucose

is released into the blood for use by other tissues such as the brain and red blood cells

absent

glucose 6-phosphatase is ___ in most other tissues

transferase and alpha-1,6-glucosidase

in glycogen degrdation, these debranching enzymes are needed for the breakdwon of glycogen

transferase

in glycogen degrdation, a ____ shift a small oligosaccharide near the branch point to ta nearby chain, thereby making the glucose moieties accessible to the phosphorylase

alpha-1,6-glucosidase

in glycogen degradation, this debranching enzyme cleaves the alpha-1,6 bond (after the transferase) at the branch point, releasing a free glucose

glycogen phosphorylase

is the key regulatory enzyme for glycogen degradation in the liver

phosphorylated

in the liver, the phosphorylase a differs from the phosphorylase b form in that a serine residues is ____

R state

T state

in regulation of glycogen degrdation in the liver, the phosphorylase a is in the ____ and the phosphorylase b is in the ____

a form

R state

the allosteric refulation fo the liver phosphorylase, the default form of the phosphorylase is the ____ in the _____

b form

T state

the allosteric refulation of muscle phosphorylase, the default form of the phosphorylase is the ___ in the ____

glucagon and epinephrine

in the muscle phosphorylation si stimuylated by the hormones ____

glucagon

the primary trigger for ____ is low blood glucose (released by pancreatic alpha-cells)

epinephrine (adrenalin)

the primary trigger for ____ is acute stress, exercise, or severe hypoglycemia (“fligh-or-flight”)

G-protein coupled glucagon receptor (GCPR)

the receptor types of glucagon

beta2-adrenergic and alpha1-adrenergic receptors

the receptor type of epinephrine is primarily ____

PKA

the hepatic mechanism of glucagon activates ___ to stimulate glycogen breakdown and inhibit synthesis

cAMP

cytosolic calcium

the hepatice machanism for epinephrine elevates ___ via beta 2 and ____ via alpha1 to trigger output

glycogenolysis

gluconeogenesis

the glucose production path for glucagon has sustained ___ and robust _____

glycogenolysis

gluconeogenesis

the glucose production path for epinphrine has rapid initial ____ that wanes, shifting to sustained ____

nonreducing ends

the ___ of the gylcogen molecule form the surface of the glycogen granule

glycogenin

at the core og the glycogen molecule is the protein ____

phosphoglucosmutase

the reaction where glucomutase converts glucose 1-phophate to glucose 6-phosphate is catalyzed by ____

a phosphoryl group is transferred from the enzyme to the substrate, and a different phosphoryl group is transferred back to restore the enzyme to its initial state

how does the enzyme glucomutase convert glucose 1-phosphate to glucose 6-phosphate?

phoaphorylase a

is phosphorylated on serine 14 of each subunit in glycogen degrdation

phosphorylase b

this phosphorylase is not phosphorylated and exists predominantyl in the T state in glycogen degrdation

high

____levels of ATP tells the system there is enough energy so the R state become the T tate (glycogen breakdown will not happen)

phosphorylase a

is a phosphorylated on serine 14 of each subunit; this modification favors the structure of the more active R state

phosphorylase b

is not phosphorylated and exists predominatly in the T state; notice that the catalyic sites are partl occluded in the T state

glucagon

stimulates glycogen breakdown in the liver when blood glucose is low

apinphrine

enhances glycogen breakdown in muscle and the liver to provide fuel for muscle contraction

G protein

transmits the signal for the initiation of glycogen breakdown

hormone

glycogen degradation is stimulated by ___ binding to 7TM receptors; its binding initiates a G-protein-dependent signal-transduction pathway that results in the phosphorylation and activation og glycogen phosphorylase

epinphrine

in addition to glucagon, ___ can activate glycogen degradation in the liver by having it bind to 7TM-alpha-adrenergic receptor to induce the phosphoinositide cascade

1) no epinphrine or glucagon

2) the inherent GTPase activity of the G protein renders these proteins inactive

3) phosphodiesterase converts cAMP into AMP, which does not stimulate protein kinase

4) protein pphosphatase 1 removes phosphoryl groups from phophorylase kinase and glycogen phosphorylase, thereby inactivating the enzymes

4 way glycogen degradation is turned off by several mechanisms:

PP1

is an important phosphatase that regulates whether glycogen will be dagraded or synthesized

UDP- glucose pyrophosphorylase

is the monomer that is used to extend the glycogen chain in synthesis

pyrophosphate

synthesis of UDP-glucose is driven by the hyrolysis of ____

UDP-glucose

glycogen synthesis

this reactiongoes from reversible to irreversible by the hydrolysis of pyrophasphate driving the reaction to produce ____ and thus ____

mutase reaction

in glycogen synthesis, glucose 6 phosphate needs to be made into glucose-1-phosphate through a ____ which then can make glycogen

primer

in glycogen synthesis, before UDP-glucose can be transferred to a growing chain of glycogen a ___ is needed

glycogenin

the primer fo glycogen synthesis is synthesized by ____, a dimer of teo identical subunits

10-20

glycogen synthesis, each subunit of glycogenin generated an oligosaccharide of glucose residues ___ molecules long

UDP-glucose

tyrosine

the first ste in glycogen synthesis is the transfer fo a glucose unit from ____ to a ____ in glycogenin

glycogenin

autocatalytically extends the glucan chain ~7 Glc units, then glycogen synthase takes over along with glycogen branching enzyme

glycogen synthase

in step 3 of glycogen synthesis _____ catalyzes the transfer of glcose from UDP-glucose to a growing chain

branching enzyme

in step 4 of glycogen synthesis ___ adds glucosyl groups to create the alpha-1,6 bond

glycogen synthase

is the key regulatory enzyme in glycogen synthesis; trnasfers a glucose moiety from UDP-glucose to the C-4 terminal residue of a glycogen chain to form an alpha-1,4-glycosidic bond

glycogen

is an efficient storage form of glucose

glycogen synthesis

is an energy driven process: two molecules of ATP are required to incorporate dietary glucose into glycogen

glycogen degrdation

the complete oxidation of glucose derived from glycogen yields 31 molecules of ATP instead of 30 because it sby pass hexokinase reaction