The average American diet contains 350-600 grams of carbohydrates. Thegovernmental suggestion is that 60% of calories should come from carbohydrates.  The body is only able to store 375-475 of these in the form of glycogen in the body.  This 1500-2000 calorie storage is enough to power a 20 mile run.  I will not go in to it here, however I must strongly state that I am completely against anyone consuming this amount of carbohydrates and also strictly oppose the government’s food recommendations.

Glycogen is a compact package of energy stored in the muscles so that when glucose is needed to produce ATP, the package is opened and glycoslysis may proceed.  Since glycogen is less compact that fats, the body preferentially burns the glycogen first.

When glycogen stores are low, the body will use glucose in the blood to refill these stores after immediate fuel needs are met.  Glycogen storage is an insulin dependent process since insulin activates glycogen synthase and other essential enzymes.  Glygogen synthase adds glucose molecules to existing primer chain. The chains are wrapped up in a smaller package and stored.

Stored glycogen in a liver cell (1) glycogen, (2) nuclei {}

Stored glycogen in a liver cell (1) glycogen, (2) nuclei {}

Glycogen usage is stimulated by the absence of insulin and by glucagon.  Glucagon is an antagonist to insulin and is secreted when blood sugar is below normal range.  Glucagon causes the liver to convert stored glycogen to glucose to then be used by the cells for energy.

When the body is in need of glucose, glycogen is cleaved by the enzyme glycogen phosphorylase.  A  debranching enzyme removes branches and reshapes it to glucogen-6-phospate where it can then be used in glycolysis, enter the pentose phosphate pathway, or be used in gluconeogensis in the liver or kidneys.

Insulin Post Table of Contents