Glycogenolysis vs Gluconeogenesis
Glycogenolysis and Gluconeogenesis are two types of processes that increase the glucose level in the blood. Liver is responsible for these two processes taking place, especially when blood glucose level decrease during the periods of fasting, and during exercise, where glucose is rapidly consumed to produce ATP. However, blood concentration of the body is also regulated by the hormones insulin and glucagon.
Gluconeogenesis is the process of producing glucose from non-carbohydrate sources. During the gluconeogenesis pathway, 6 ATP molecules are consumed per molecule of glucose produced. It mainly occurs in hepatocytes in liver. In these cells, most reactions of the gluconeogenesis take place in the cytoplasm while two reactions occur in the mitochondria. The molecules that provide substrates for gluconeogenesis include proteins, lipids and pyruvate. Pyruvate is produced by glycolysis under anaerobic conditions. Muscle proteins are degraded to form amino acids, some of which used in gluconeogenesis. These amino acids are called ‘glucogenic amino acids’. When consider the lipid substrates, glycerol produced during the hydrolysis of fat stores or ingested fats are used in gluconeogenesis. Propionyl CoA; a product of β-oxidation of odd-numbered fatty acids also participate in gluconeogenesis. However, fatty acids do not involve directly as a substrate during gluconeogenesis.
This is the process of glycogen breakdown to form glucose molecules. Glycogenolysis occurs in the cytoplasm and is stimulated by glucagon and adrenaline hormones. The two steps of glycogenolysis are; strand- shortening, during which glycogen polymer breaks into short strands via phosphorolysis, and branch removal, during which free glucose is produced by debranching of glycerol. The enzymes required for this process are glycogen phosphorylase, debranching enzyme, and amylo-α-1, 6-glucosidase.
What is the difference between Glycogenolysis and Gluconeogenesis?
• Gluconeogenesis is the production of glucose from non-carbohydrate sources, whereas glycogenolysis is the process of glycogen breakdown.
• During glycogenolysis, glycogen is broken down to form the glucose-6-phosphate, and during gluconeogenesis, molecules such as amino acids and lactic acids convert into glucose.
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