Glükogenolüüsiga

Glükogenolüüsiga, meaning glycogenolysis in English, is a metabolic process that breaks down glycogen into glucose. Glycogen is a storage form of glucose found primarily in the liver and muscles. This process is crucial for maintaining blood glucose levels and providing energy during periods of fasting or increased physical activity.

The breakdown of glycogen begins with the enzyme glycogen phosphorylase, which removes glucose units from the glycogen chain. These released glucose units are then converted into glucose-1-phosphate. In the liver, glucose-1-phosphate is further converted to glucose-6-phosphate, which can then be dephosphorylated by glucose-6-phosphatase to release free glucose into the bloodstream. This free glucose is essential for supplying energy to organs, particularly the brain, when dietary intake is insufficient.

In muscle cells, glycogenolysis serves a slightly different purpose. While glucose-6-phosphate is also produced, muscle cells lack the enzyme glucose-6-phosphatase. Therefore, the glucose released from muscle glycogen is primarily used within the muscle itself for energy production during muscle contraction. This localized energy source is vital for physical exertion.

Hormonal regulation plays a key role in controlling glycogenolysis. Glucagon, a hormone secreted by the pancreas, stimulates glycogenolysis in the liver when blood glucose levels are low. Adrenaline (epinephrine), released by the adrenal glands during stress or exercise, also promotes glycogenolysis in both the liver and muscles. Conversely, insulin, another pancreatic hormone, inhibits glycogenolysis while promoting glycogen synthesis (glycogenesis). This intricate hormonal balance ensures that glucose is available when needed and stored efficiently when in excess.