Glukoneogeneza

Glukoneogeneza is a vital metabolic pathway responsible for the synthesis of glucose from non-carbohydrate precursors. This process occurs primarily in the liver and, to a lesser extent, in the kidneys, and is crucial for maintaining blood sugar levels during fasting, strenuous exercise, or low-carbohydrate intake.

The main substrates for glukoneogeneza include lactate, certain amino acids (like alanine), and glycerol. Lactate is produced by muscles during anaerobic respiration, while glycerol is released from the breakdown of fats in adipose tissue. The pathway essentially reverses many steps of glycolysis, but it bypasses three irreversible reactions through unique enzymes. These key enzymes are pyruvate carboxylase, phosphoenolpyruvate carboxykinase (PEPCK), fructose-1,6-bisphosphatase, and glucose-6-phosphatase.

Glukoneogeneza is energetically expensive, consuming six ATP molecules to produce one glucose molecule from two pyruvate molecules. The pathway is tightly regulated by hormones to prevent it from operating simultaneously with glycolysis, which would create a futile cycle. Glucagon is the primary hormone that stimulates glukoneogeneza during fasting, while insulin suppresses it when blood glucose is high.

This process is essential for providing glucose to glucose-dependent tissues, such as the brain and red blood cells, ensuring a continuous energy supply even in the absence of dietary carbohydrates.