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Glossary of BioChem: Gluconeogenesis

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About how many grams of glucose are used by humans every day?
How much of this goes to the brain?
Body fluids?
-160g
-75% or 120g!
-20g to body fluids
How many grams of glucose can glycogen store?
-160-180g
What is Gluconeogenesis?
-the synthesis of glucose from non-carbohydrate sources when it isn't available
What are the major sites of gluconeogenesis and what percent do they contribute?
-liver 90%
-kidney 10%
What are the major substrates for gluconeogenesis?
-lactate
-amino acids
-pyruvate
-TCA cylce intermediates
Glycolysis is irreversible, but gluconeogenesis can reverse them. What are the 4 new reactions?
-conversion of pyruvate to phosphoenolpyrucate (2 steps)
-going from gructose-1,6-bisphosphate to fructose-6-phosphate
-removing the phosphate from glucose-6-phosphate
For animals lacking mitochondrial PEP carboxykinase, how is OAA transported (what does this stand for)?
-Oxaloacetate is transported by the malate shuttle after converting mitochondrial OAA to malate
How does gluconeogensis reverse the phosphofructokinase reaction of glycolysis?
-it isn't reversible so gluconeogenesis bypasses it with fructose-1,6-bisphosphatase
In step three of gluconeogenesis, where it the enzyme Glucose-6-phosphatase found?
-only in the liver, kidney, pancreas, and small intestine
What are the individual energy requirements for gluconeogenesis?
-2 ATP for pyruvate carboxylase
-2 GTP for PEP Carboxykinase
-2 ATP for Phosphoglycerate kinase
-2 NADH for glyceraldehyde-3-P DH
What are the overall energy requirements for gluconeogenesis?
-6 ATP and 2 NADH to synthesize one molecule of glucose
Why is it important to control glycolysis/gluconeogenesis?
-ATP would be hydrolysed for no purpose and wasted
*one cyle is oxidation of glucose, the other is for glucose synthesis
What controls liver PFK-1?
-Fructose-2,6-bisphosphate
*graphs a nice tapering arc
What affect does Fructose-2,6-Bisphosphate have on glycolysis and gluconeogensis?
How does this work?
-activates glycolysis
-inhibits gluconeogenesis
*F-2,6-P increase the inhibition of F-1,6-P by AMP

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