Glycogen core a glycogenin protein. Glycogen in muscle, liver, and fat cells is stored in a hydrated form, composed of three or four parts of water per part of glycogen associated with 0.45 millimoles (18 mg) of potassium per gram of glycogen. As a meal containing carbohydrates or protein is eaten and digested, blood glucose levels rise, and the pancreas secretes insulin. Blood glucose from the portal vein enters liver cells (hepatocytes). Insulin acts on the hepatocytes to stimulate the action of several enzymes, including glycogen synthase. Glucose molecules are added to the chains of glycogen as long as both insulin
Glucose cycle Glucose cycle The glucose cycle (also known as the hepatic futile cycle) occurs primarily in the liver and is the dynamic balance between glucose and glucose 6-phosphate. This is important for maintaining a constant concentration of glucose in the blood stream. The glucose cycle is required for one of the liver functions; the homeostasis of glucose in the blood stream. When the blood glucose level is too high, glucose can be stored in the liver as glycogen. When the level is too low, the glycogen can be catabolised and glucose may re-enter the blood stream. The catabolic process occurs at