carbohydrate metabolism I Flashcards
Glucose transporters:
GLUT1
GLUT2 (only in cells and are highly regulated)
GLUT3
GLUT4 (only in cells and are highly regulated)
GLUT2
low affinity transporter in hepatocytes and pancreatic cells.
captures glucose for storage
when [Glu]
GLU4
is in adipose tissue and muscle and responds to glucose concentration in peripheral blood.
insulin increases the rate of glucose being transported between the adipose tissue and the muscle
Km is close to normal glucose levels (~5mM)
Which means that the transporter is saturated when blood glucose levels are just a bit higher than normal
a lot of insulin = increases GLUT4 transporters available
a decrease in insulin = decreases the amount of GLUT4 transporters available
Glycolysis
occurs in the cytoplasm of all cells, and does not require oxygen
yields 2 ATP per molecule of glucose
Glucokinase
Glycolytic enzyme
converts glucose to glucose 6 - phosphate
Present in the pancreatic beta - islet cells as part of the glucose sensor and is responsive to insulin in the liver
Hexokinase
Glycolytic enzyme
converts glucose to glucose 6 - phosphate in peripheral tissues
Phosphofructokinase- 1 (PFK-1)
Glycolytic enzyme
phosphorylates fructose 6-phosphate to fructose 1,6-bisphosphate in the rate limiting step of glycolysis.
PFK1 is activated by AMP and fructose 2,6-bisphosphate (F2,6-BP) and is inhibited by ATP and citrate
Phosphofructokinase- 2 (PFK-2)
Glycolytic enzyme
produces the F2,6-BP that activated PFK-1.
It is activated by insulin and inhibited by glucagon
Glyceraldehyde-3-phosphate dehydrogenase
Glycolytic enzyme
produces NADH, which can feed into the electron transport chain
3-phosphoglycerate kinase and pyruvate kinase
Glycolytic enzyme
each perform substrate - level phosphorylation placing an inorganic phosphate (Pi) and ADP to form ATP
