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73 Cards in this Set

  • Front
  • Back
basal glucose uptake transporters found in all mamailan tissues
GLUT 1 and GLUT 3
membrane transporter that uses active transport
membrane transporter found only in the liver and pancreatic B cells
transporter that has a HIGH Km for glucose
which transporter carries glucose out into the bloodstream when entrocyte glucose levels get high
where is insulin released from
Pancreatic B cells
which transporter is cotrolled by Insulin?
where are GLUT 4 transporters found?
adipose tissues (fat cells) and skeletal muscle
how do skeletal muscle and adipose tissue store glucose
glycogen and fat
which transporters uptake fructose?
two transporters on apical side of intestine cells?
GLUT 5 and SGLT1
expressed in tumor cells and induces GLUT 1 and GLUT 3 and key enzymes in glycolysis
HIF- 1 Hypoxia Inducible Transcription Factor
how does the cell trap glucose?
hexokinase and glucokinase
converts glucose to G6P in all tissues
convert glucose to G6P in liver and Pancreatic B Cells
which has higher Km for glucose? Hexokinase or Glucokinase?
hexokinae- .1nM
glucokinase- much higher
what does hexokinase use as a substrate and why?
Mg-ATP...neutralizes negative charge of ATP
how does cell shut off hexokinase?
is inhibited by G6P
where is glucokinase present?
Liver and Pancreatic B Cells
The 3 fates of G6P
glycolysis, glucose, pentose phosphate
glycogen linkages
alpha (1,4) and alpha (1,6)
why store as glycogen and not glucose?
extreme osmotic advantage
one free reducing end in glycogen is added to
major enyme that breaks down glygogen
glycogen phosporylase breaks glycogen down to...
cofactor that works with glycogen phosphorylase
pyridoxal phosphate
product left by glycogen phosphorylae
limit dextrin
breaks down limit dextrins
Debranching Enzyme
converts G1P to G6P
Phosphoglucomutase adds P using which amino acid?
takes P off of G6P
Glucose-6- Phosphatase
where is Glucose-6- Phosphate located?
luminal surface of ER
path of glucose to get the P taken off
1)goes to ER to be acted on by Glucose 6-Phosphatase
2) back to cytosol
3) builds up inside liver cell
4)diffuses back into blood through GlUT 2 transporters
why is it advantageous for liver to have glucokinase?
If had hexokinase, all of glucose would be Phosphorylated right away- need some to go out in the blood
How does Debranching enzyme work
1) Take a piece off of alpha (1,6) branch and installs it in another place
2) Hydrolysis step- takes last part of branch that is left...uses water and FREE GLUCOSE is released
where could someone without Glucose 6 Phosphatase still get glucose?
1 free glucose released by Debranching Enzyme
why is Glycogen Phosphorylase rxn not reversibe?
because of low ratio of G1P campared to P ratio.
G6P to G1P
GIP is activated by
UDP- Glucose Pyrophosphorylase
what is cofactor used to drive the UDP- Glucose Pyrophosphorylase reaction forward
Pyrophosphatase (splits pyrophosphate irreversibly).
catalyzes the elongation of non-reducing termini of glycogen
Glycogen Synthase
what type of linkages does Glycogen Synthase form?
alpha (1,4)
how long does chaing have to be for glucose to be added to glycogen chain by Glycogen Synthase? attached to which structure?
4 units
UDP glucose specifically
Glycogen Synthase is dephosphorylated (activated) by which enzyme?
generalized enzyme that regenerates triphosphate molecules with the use of ATP
nucleoside diphosphate kinase
small protein that is a dimer at the center of glycogen molecule
glycogenin contains what residue?
glycogenin attaches how many glucose molecules? what is donar?
UDP glucose
after glycogenin and glycogen synthase have made chain at least ll units, which enzyme takes over?
Branching Enzyme
how does Branching Enzyme work?
can move a 7 glucose unit chain to a 6 position on a nearby chain...can't be closer than 4 units to another branch.
Two VERY important enzymes that control blood glucose
Glycogen Phosphorylase
Glycogen Synthase
Things that increase glycogen breakdown
Things that increase glycogen syntheis (4(
active state of glycogen phosphorylase
R state
inactive state of glycogen phosphorylase
T state
hormones that control glycogen phosphorylase (glucagon, epinephrine, and insluin) work through:
Phosphorylase Kinase
takes off phosphate (opposes phosphorylase kinase)
Protien Phsopate 1 (pp1)
what is allosteric effector that can force phosphorylase a back into the inactive state (T state)
what is allosteric effector rhat can force phosphorylase b to the active state?
AMP (signal that cell is using ATP- need more energy- must break down glycogen)
mediator between phosphorylase b to phosphorylase a
Phosphorylase Kinase
Phosphorylase Kinase must be activated
1) being phosphorylated itself in the B subunit
2) Calcium binging to the sigma subunit
what phosphorylates Phosphorylase Kinase?
Protein Kinase A
(cAMP dependent protein kinase)
catalyzed the undoing of phosphorylation by Protein Kinase A and phosporylase Kinase
cAMP dependent cascade
(in box)
epinephrine- adenylate cyclase-cyclic AMP-Protein Kinase A
2 additional steps for glycogen breakdown
Phosphorylase Kinase- Phosphorylase a
additional stop for glycogen synthesis
Phosphorylates (deactivates) Glycogen Synthase...forms Glycogen Synthase Bi
How else does epinephrine initiate glycogen breakdown?
inhibits pp1....acts on Protein Kinase A to phosphorylate a binding protein..relases pp1.....also phosphorylates inhibitor-really shuts down pp1
How does insulin stimulate glycogen breakdown?
phosphorylates binding molecule in a different place..makes glycogen more accessible by pp1
Two things that pp1 does to initiate glycogen synthesis
forces Glycogen Phosphorylase A to form Glycogen Phosphorylase B (inactive state) by dephosphorylation
2) also dephosphorylates Glycogen Synthase (act9vates)
when is pp1 activated
when Glycogen Phosphorylase a is in the T State...phosphate is exposed and pp1 dephosphorylates it
what mediates the stimulation of gluconeogenesis in the liver by glucagon and epinephrine?
what recruits GLUT 4s to membrane in skeletal muscles for glucose uptake?
Calcium in muscles cells activate what to stimulate glycogen breakdown in muscle cells?
phosphorylase kinase