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Biochemistry Ch 15,16,17

Terms

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What is GLUT1?
-glucose transporter
-all mamalian species
-basal glucose uptake
What is GLUT2?
-Liver and pancreatic beta-cells
-in pancreas plays role in insulin regulation
-in liver removes excess glucose from blood
GLUT3
-all mammalian species
-basal glucose uptake
GLUT4
-muscle and fat cells
-amount in muscle plasma membrane
GLUT5
-small intestine
-increases with endurance training
-primarily a fructose transporter
Stage one of Glycolysis
-glucose-> fructose-1,6-bisphosphate
-phosphorylation, isomerization, phosphorylation
Stage two of Glycolysis
aldolase
F-1,6-BP --> DHAP + GA-3-P
triose phosphate isomerase
DHAP--> GA-3-P
Stage 3 of Glycolysis
GA-3-P<-->1,3-bisphosphoglycerate
1,3-BPG<--> 3-PG +ATP
3-PG<--> 2-PG
2-PG<--> PEP
PEP---> pyruvate + ATP
NET RXN glucose--> pyruvate
Glucose + 2 Pi + 2 ADP + 2 NAD+ ------->
2 pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O
NET 2 ATP
NADH in glycolysis-areobic
Under areobic conditions, the NADH generated during glycolysis is used to fuel mitochondrial ATP synthesis via oxidative phosphorylation producing either 2 or 3 equivalents of ATP depending on whether the glycerol phosphate or the malate-aspartate shuttle is used to transport the electrons from cytoplasmic NADH into the mitochondria. This cycle creates a continuous pool of cytoplasmic NAD+ essential for glycolysis to continue.
NADH in glycolysis-aneorobic
pyruvate is converted to lactate by lactate dehydrogenase:
Pyruvate + NADH + H+-->Lactate + NAD+
This reduction is essential to form NAD+ for the glceraldehyde-3-phosphate dehydrogenase reaction, without which glycolysis will stop.
Phosphofructokinase 1
Liver enzyme – Inhibitors; high levels of ATP and citrate (citrate enhances the inhibitory
effect of ATP)
Activator, F-2,6 BP (binding of F-2,6 BP increases the affinity of PFK 1 for F-6-PO4 and
decreases the inhibitory effect of ATP)
Phosphofructokinase 2
Fructose-2-6-BP is an important regulator of glycolysis because it is an allosteric activator of PFK I. It is synthesized from F-6-P and ATP by the action of phosphofructokinase 2 (PFK 2). PFK 2 is a bifunctional enzyme, housing both the kinase and phosphatase (FBPase 2) activities on a single polypeptide chain. FBPase 2 hydrolyzes F-2,6-BP to form F-6-P and Pi.

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