Liver glycogen Flashcards
What is the importance of storing glycogen
need it in order to raise blood sugar, glucose for the brain. better source compared to protein or fat
What is the structure of glycogen. Where in the body stores a lot of glycogen.
liver and muscles, its a highly branched polymer there are way more alpha 1,4 linkages than alpha 1,6.
Glycogen has more alpha 1,6 or alpha 1,4 linkages
alpha 1,4 !!
why is it beneficial for glucagon to stimulate both glcogenolysis and gluconeogenesis in liver cells?
both processes add sugar to the blood
liver cells have an enzyme that others don’t; they take a phosphate off the glucose and export it. once phosphate is remove the glucose is exportable. the enzyme is glucose 6 phosphatase.
What is the reaction catalyzed by phosphoglucomutase
not a control point, its a step in glycogenolysis and glycogensis.
glucose 1P to glucose 6P
How are glycogenesis and glycogenolysis are not exact reversals of one another.
its advantageous to not have exact enzymes,. rates are seprately controlled at each step. liver slows down one pathway while it speeds up another. more control this way
name a compound that is the donor of glucose rings to a variety of building products.
UPD glucose
hexokinase
phosphorylation of glucose for muscle
glucokinase
phosporylation of glucose in the liver
phosphoglucomutase
moves phosphate from position one to position 6,
UDP glucose (full name)
uridine diphosphate UDP glucose - reaction produces fthis form glucose 1 phosphate
describe reaction catalyzed by glycogen synthase
UDP glucose donates a glucose to glycogen and glycogen gets one glucose bigger. catalyzes alpha 1,4 linkages.
describe the need for brancher enzyme
alpha 1,6 branching enzyme works to remodel glycogen. doesn’t make glycogen longer though
glycogen phosphorylase
important for glycogenolysis. it can break the 1,4 linkage to remove a glucose. its a phosphorolysis reaction. a PPi breaks the linkage
debrancher enzyme
catalyzes hydrolysis of 1,6 linkages. water breaks the linkages. small amount relative to the 1.4 linkages
glycogen phosphorylase cofactor
PLP (ODD but its here)
How is PLP formed ?
from B6. oxidation followed by dehydrogenase. primary alcohol oxidized to an aldehyde. then a kinase transfers a phosphate from an ATP.
Glycogen metabolism in response to insulin signals
speed up, slow down glycogenolysis
glycogen metabolism in response to glucagon
glycogenolysis speed up and glycogenesis slows down
glycogen metabolism in response to epinephrine
glycogenolysis speed up - during exercise, think about epinephrine and how this would need to break down glycogen
glycogen metabolism and increase in cAMP or calcium
glycogenolysis speeds up - think about muscle cells
Describe regulation of glycogen metabolism by glucagon and insulin.
glucagon signals in the fasting state will be undone by insulin in the fed state.
if glycogen synthetase gets phosphorylated it gets inactivated. (protein kinase A which is activated during glucagon)
if glycogen phosporylase- activated
glycogen synthase
make glycogen, activated with insulin
glycogen phosphorylase
breaks down glycogen. activates phosphorylase kinase
