True about gluconeogenesis
Gluconeogenesis: Gluconeogenesis is the formation of glucose from non-carbohydrate sources. Gluconeogenesis helps to maintain the glucose level in the blood, so that the brain, RBC, and muscle can extract glucose from it to meet their metabolic demands when dietary glucose is low. This process is very much necessary in the body because brain and RBC utilizes only glucose as energy fuel. The major non-carbohydrate precursors of glucose are lactate, glucogenic amino acids (all except leucine) and glycerol. Lactate is formed by RBC in glycolysis because mitochondria are absent. Lactate is also formed by active skeletal muscle when the rate of glycolysis exceeds the rate of TCA cycle, the pyruvate formed is conveed to lactate. Amino acids are derived from proteins in the diet and during starvation, from the breakdown of proteins in skeletal muscle. Glycerol is derived from the hydrolysis of triacylglycerol's (TAG). Gluconeogenesis occurs mainly in liver and kidney. It also occurs in brain and muscle to some extent. Gluconeogenesis occurs during (1) Starvation, (2) To clear lactate formed in RBC and muscle, (3) When carbohydrates in the diet are low, (4) Pregnancy, (5) Lactation, (6) Febrile diseases. Gluconeogenesis is almost the reversal of glycolysis excepting at three steps which are irreversible in glycolysis. These steps are reversed by enzymes known as the key enzymes of gluconeogenesis i.e. those enzymes specific for gluconeogenesis only but not for any other pathway.Ref: DM Vasudevan, 7th edition, page no: 117
Occurs mainly in muscle
It is reverse of glycolysis
Alanine & lactate both can serve as substrate
Glycerol is not a substrate
Metabolism of carbohydrate