Glycogen, a polymer of the sugar glucose, functions as both a reserve of energy and a structural building block in organisms from bacteria to humans. It is synthesized when nutrients are available for utilization in times of need. In mammals, the two largest deposits of glycogen are in skeletal muscle and liver; muscle glycogen is utilized locally to help fuel muscular activity, whereas liver glycogen is broken down to glucose that is delivered into the bloodstream. After a meal, elevated blood glucose causes the hormone insulin to be released from the pancreas and to stimulate conversion of ingested glucose into glycogen in muscle, liver, and other tissues. Upon fasting, such as overnight, the pancreatic hormone glucagon signals the breakdown of liver glycogen to stabilize blood glucose levels, essential for brain function. The hormone epinephrine stimulates glycogen breakdown in liver and muscle to cope with stressful situations.
- Glucose homeostasis
- Glycogen storage diseases
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)