Lecture 19 Flashcards
glucose is stored as what in humans
glycogen
reasons for storing glucose as glycogen
breakdown can provide energy for muscle very quickly, liver stored glycogen can regulate blood glc levels, some muscles and cells have to have glucose
level 1 structure of glycogen
1-4 alpha glycosidic linkage
level 2 structure of glycogen
beta particle
level 3 structure of glycogen
alpha particles
breakdown of cellular glycogen to glucose 1 phosphate
glycogenolysis
synthesis of glycogen
glycogenesis
first step of glycogenesis
glucose to glucose 6 phosphate
enzyme in first step of glycogenesis
hexokinase
second step in glycogenesis done by what
phosphoglucomutase
second step in glycogenesis
glucose 6phos -> glucose 1,6 bisphos -> glucose 1 phos
what does third step in glycogenesis start with
sugar phosphate + NTP
what does third step in glycogenesis end with
UDP glucose pyrophosphorylase enzyme, pyrophosphate
enzyme in third step of glycogenesis
NDP sugar phosphorylase
what happens after third step of glycogenesis
elongation of glycogen chains
catalyzes formation of alpha 1-6 bonds found at branch points of glycogen cleaves off part of existing straight glycogen chain
glycogen branching enzyme
what does glycogen synthase require
a primer
primer on which new chains are assembled and the enzyme that catalyzes their assembly
glycogenin
what does glycogenin use as a substrate
UDP glc
catalyzes phosphorolytic cleavage at the nonreducing ends of glycogen ends of glycogen chains
glycogen phosphorylase
what does glycogen phosphorylase break down
alpha 1-4 glc bonds
what does glycogen phosphorylase yield
GLC 1- phos
what does glycogen phosphorylase require
pyridoxal phosphate
how many glc units in one molecule of glycogen
55000
transfers branches onto main chains and releases residue at 1-6 alpha branch as FREE clc
debranching enzyme
catalyzes reversible rxn from glucose 1 phos to glucose 6 phos
phosphoglucomutase
what happens to glucose 6 phos in muscle
enters glycolysis
what happens to glucose 6 phos in liver
converted to glucose to regulate blood glucose levels
hormone that creates glycogen
insulin
anabolic high blood clc homorne
insulin
what does insulin activate
phosphoprotein phosphates, glycogen synthase
what does insulin inactivate
glycogen phosphorylase
breaks down glycogen
glucagon
glycogen activates what
protein kinases, glycogen phosphorylase
glucagon inactivates what
glycogen synthase
2 forms of glycogen synthase
glycogen synthase a and B
which form of glycogen synthase is unphosphorylated and catalytically active
a
which form of glycogen synthase is phosphorylated and inactive unless glucose 6phos is present
b
catalyzes phosphorylation of glycogen synthase a
glycogen synthase kinase 3
insulin does what to GSK3 and PP1
inactivates GSK3, activates PP1
GSK3 adds what
3 phosphates from ATP
2 forms of skeletal glycogen phosphorylase
glycogen phosphorylase a and b
which form of glycogen phosphorylase is catalytically active
a
what two things trigger phosphorylation of phosphorylase b
epinephrine and glucagon
signal for muscle contraction
Ca2+
what does Ca2+ bind to
phosphorylase b kinase
what accumulates in contracting muscle
AMP
removes phosphoryl groups from phosphorylase a, converting it to phosphorylase b
phosphoprotein phosphatase 1
which is a glucose sensor
liver glycgen phosphorylase A
sequence of enzymatic rxns in which a catalyst aactivates a catalyst activates a catalyst
enzyme cascade
rise in cAMP activates what
PKA
catalyzes phosphorylation of glycogen phosphorylase b
phosphorylase b kinase
