University:
Liberty University
Course:
BIOM 500 | Introduction to Biomedical Sciences
Academic year:

2024
Views:

181

Pages:

5
Author:

Sheha A.

Gluconeogenesis It is the process of formation of glucose from various non-carbohydrate sources such as the gluconic acid, amino acids, lactate, pyruvate, glycerol, and propionate. It occurs in the fasting state or low carbohydrate diet in livers or some tissues. Site: cytosol This will provide continuous supply of glucose as source of energy for the CNS, brain, RBC and skeletal muscle during starvation. Pathway involves steps of TCA cycle and several key enzymes involved. Key enzymes involved: Pyruvate carboxylase, phosphoenol pyruvate carboxykinase, fructose 1,6-bisphosphatase, and glucose-6-phosphatase. Regulation of Gluconeogenesis Glucagon and glucocorticoids increase the rate of gluconeogenesis by inducing the enzymes and insulin decrease the rate of gluconeogenesis. Glucagon inactivates pyruvate kinase through cAMP dependent phosphorylation. Acetyl CoA promotes gluconeogenesis. Starvation results in excessive lipolysis in adipose tissue. The fatty acids released are oxidized and acetyl CoA accumulates in liver; this acetyl CoA stimulates the gluconeogenic enzymes. Glucagon reduces the concentration of fructose 2,6-bisphosphate so that PFK-1 remains inactive and activates fructose 1,6-bisphosphatase that increases gluconeogenesis. Substances for Gluconeogenesis Lactate and Glycerol (component of gluconeogenesis) Amino acids Glucogenic amino acids (component of gluconeogenesis) Alanine, serine, threonine, cysteine, glycine, proline, arginine, histidine, glutamate Aspartate Valine, isoleucine, methionine Arginine, Histidine, Glutamine, Proline Phenylalanine, Isoleucine, Threonine, Tryptophan, Leucine, Lysine Aspartate, glutamate Succinyl CoA Acetyl CoA Significance: Maintaining blood glucose level: Gluconeogenesis provides glucose when carbohydrate is not available in sufficient amount from the diet or from glycogen reserve. Clear the products of metabolism: Maintain metabolites produced in the tissues accumulate in the blood. These metabolites are cleared by the gluconeogenesis. e.g. Lactate from muscle and RBC’s by Cori cycle