Ch. 9: Carbohydrate Metabolism I Flashcards
what drives glucose entry into the cells
concentration
where is GLUT 2 located
hepatocytes and pancreatic cells
what does GLUT 2 do
captures excess glucose from the digestive tract primarily for storage
when does GLUT 2 function
when blood glucose levels are high until the concentration drops below the Km T (which is high) for the transporter
where is GLUT 4 located
adipose tissue and muscle
how does GLUT 4 function with insulin
when insulin is high, transporters move from inside cell to membrane
how high is the Km of GLUT 4 in relationship to nl blood glucose levels
Km is slightly higher than normal blood glucose
what does GLUT 4 do
captures excess blood glucose for for storage in muscles (as glycogen) and adipose tissue (DHAP)
what occurs (big picture) during glycolysis
- glucose is converted into two pyruvate molecules
- which release energy that
- is captured in two substrate level phosphorylations and
- one oxidation reaction
how are the products of glycolysis used by the body (big picture)
if oxygen + mitochondria, NADH feeds into aerobic respiratory pathway
if no oxygen or mitochondria, anaerobic energy
sometimes, intermediates for other pathways
what do hexokinase and glucokinase do
phosphorylate glucose inside the cell to prevent it from leaving the cell via the transporter
where is hexokinase located
most tissues (GLUT 4)
where is glucokinase located
hepatocytes and pancreas cells (GLUT 2)
what does phosphofructokinase-1 do
rate-limiting enzyme and main control point in glycolysis
phosphorylates fructose
activated (turns on glycolysis) by AMP and citrate and inhibited (turns off glycolysis) by ATP
what does phosphofructokinase-2 do
phosphorylates F6P to F26P, which activated PFK-1
what does glyceraldehyde-3-phosphate dehydrogenase do
catalyzes an oxidation and addition of inorganic phosphate to its substrate –> high energy intermediate: 1,3 - biphosphoglycerate
reduces NAD+ to NADH
what does 3-phosphoglycerate kinase do
transfers the high-energy phosphate from 1,3 - biphosphoglycerate to ADP –> ATP
substrate-level phosphorylation
what occurs during substrate-level phosphorylation
ADP is directly phosphorylated to ATP using high energy intermediate
not oxygen dependent, like oxidative phosphorylation
what does pyruvate kinase do
catalyzes substrate-level phosphorylation of ADP –> ATP and pyruvate