Part 2 - lecture 1.2 - Quiz Flashcards
(28 cards)
Which glucose transporter is bidirectional and why?
GLUT2 - liver, pancreas, intestine and kidney - liver and kidney need to be able to deliver glucose out or they would not be able to share it with the environment
What is the most general glucose transporter?
GLUT1 - found essentially everywhere
Which glucose transporter is insulin dependent and stimulates muscle and adipose tissue?
GLUT4 - muscle and adipose need to tatke up extra glucose when insulin signals because it needs it for storage
Which enzymes are regulated in glycolysis?
Hexokinase, PFK1 and pyruvate kinase
In what two ways do hormones regulate activity?
By phosphorylation activities or by gene expression level of an enzyme
In what two ways are glycolytic enzymes regulated?
Small MW effectors and hormones
Does hexokinase or glucokinase have a higher Km?
Glucokinase - specific for glucose is turned on when circulating levels are too high
What happens to glucose in the liver?
It can be stored or converted to FAs or modified
What is hexokinase inhibited by? why is this important?
It’s product G6P - needs to be turned off so that all of the ATP is not being tied up in the liver cells causing death or damage when continuously signaled
What is glucokinase stored?
In the nucleus - bound to a regulatory protein GKRP
What is glucokinase inhibited by?
F6P (indirectly) which promotes GKRP binding
What are hexokinase and glucokinase in relation to eachother?
isoenzymes
When does glucokinase dissociate from GKRP?
WHen glucose levels increase
How is glucokinase hormonal regulated?
Inducible by insulin
What does fructose do to glucose utilization?
Gets converted to F1P by fructokinase and glucokinase is activated by F1P - causing extra glucose use for FA synthesis
What are the allosteric inhibitors of PFK1?
ATP, citrate from TCA, and H+
What are the allosteric activators of PFK1?
AMP, Fructose-2-6-BP (hormonal)
How is PFK1 hormonally regulated?
Upregulated by insulin, downregulated by glucagon
What does PFK2 do?
Produces F-2-6-BP from F6P which activates PFK1 and glycolysis
What kind of enzyme is PFK2?
Bifunctional - has kinase and phosphatase to produce and eliminate F26BP
How is PFK2 controlled by hormones?
Glucagon phosphorylates to inactivate the kinase so inactivates glycolysis
Insulin dephosphorylates activate the kinase and activating glycolysis
What does epinephrine do to PFK2 in the heart?
Phosphorylates activating the kinase and activating glycolysis
Explain the pathway of PFK1 in the liver if glucagon is high?
High glucagon to low insulin cause increased cAMP which elevates protein kinase A which phosphorylates PFK2 to make it inactivate so fructose 2-6BP isn’t made and PFK1 is not activated so gluconeogenesis instead of glycolysis is favored
Explain the pathway of PFK1 in the liver if insulin is high?
High insulin to low glucagon decreased cAMP and protein kinase A levels meaning that there is dephosphorylation of PFK2 activating the enzyme to favor the formation of F26BP which activate PFK1 to continue in glycolysis
