Lecture 10- gluconeogenesis

gluconeogenesis

glucose synthesis from non-carbohydrate precursors, maintain blood glucose during fasting and starvation, happens mainly in liver and kidney in starvation

gluconeogenesis- energy from where

fat during fasting, fatty acids broken down and go to liver

3 gluconeogenic precursors

lactate: from anaerobic glycolysis (exercising muscle or RBC); glycerol: released from adipose tissue stores; amino acids: particularly alanine produced in muscle from other AA and from glucose

precursors can form

pyruvate, TCA cycle intermediates, or intermediates common to both glycolysis & GNG

fate of lactate- cori cycle

glucose in RBC undergoes glycolysis to become lactate which goes to liver and undergoes glconeogensis to become glucose which goes to RBC and repeat

are fatty acids gluconeogenic? 

no, fatty acids can not be connected to glucose 

β-oxidation of fatty acids

oxidation of odd chain fatty acids results in a 3-carbon residue, minimal conversion of odd chain fatty acids to glucose in humans, and high conversion of propionyl-CoA to glucose in ruminants

gluconeogenesis step 1- conversion of pyruvate to PEP

several steps to bypass the irreversibility of pyruvate kinase, pyruvate carboxylase found in matrix of mitochondria, oxalocetate cannot cross inner mitochondrial membrane, converted to malate (or aspartate)

gluconeogenesis step 2- F1,6BP to F6P

F1,6 bisphosphatase releases inorganic P from F1,6BP; stimulated by high ATP levels, inhibited by high AMP and high F2,6-bisphosphate

gluconeogenesis step 3- G6P to glucose

G6P inhibited by insulin, increase low Km, converted to glucose