All of these substrates are glucogenic except:
Ans. a. Acetyl CoA (Ref: Harper 30/e p185. 29/e p187)Acetyl CoA is not a substrate for gluconeogenesis and cannot be converted back to glucose."Acetyl CoA is not a substrate for gluconeogenesis and cannot be converted back to glucoseQ. This is because acetyl CoA cannot be converted back to pyruvateQ since its carbon backbone is lost in citric acid cycle as CO2 "GluconeogenesisThe carbon skeletons for gluconeogenesis are derived primarily from glucogenic amino acids & lactate from muscle & glycerol from adipose tissuesQ.Although the lactate produced in muscle, is used by liver for gluconeogenesisQ.Liver & kidneys are the major gluconeogenic tissuesQ.Glucogenic key enzymes are expressed in small intestine but their role in fasting state is unclear.Gluconeogenesis prevent hypoglycemia during short & long term fasting.Gluconeogenesis is stimulated by excess of acetyl Co-A & decrease in fructose 2, 6 biphosphate concentrationQ.Substrates for Gluconeogenesis* Glucogenic amino acids (all except Leucine & lysine which are purely ketogenic): Most important is alanineQ* LactateQ* PyruvateQ* PropionateQ* GlycerolQ* FumarateQ
Acetyl CoA
Pyruvate
Glycerol
Lactate
Gluconeogenesis