Metabolism of glycogen includes synthesis of glycogen by glycogenesis and breakdown of glycogen by glycogenolysis. This helps to regulate the levels of glucose in the blood.
Glycogen is the animal storage form of glucose. If a person is in an anabolic state, such as after consuming a meal, most glucose within the myocytes (muscle cells) or hepatocytes (liver cells) is going to be stored as glycogen. This helps to maintain blood glucose levels. Excess glucose in the blood is converted into glycogen and is stored in the liver or muscles. The synthesis of glycogen from glucose is a process known as glycogenesis.
When the amount of glucose reduces in the blood and the body needs glucose, the stored glucose in the liver and muscle is broken down to form glucose. The process of liberating glucose from glycogen is known as glycogenolysis. This is carried out by the enzyme glycogen phosphorylase.
Practice Questions
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MCAT Official Prep (AAMC)
Key Points
• Excess glucose in the blood is converted into glycogen for storage.
• Glycogen is stored in liver and muscle cells.
• When there is a shortage of glucose, the glycogen is broken down to liberate glucose.
• Glycogen metabolism helps to maintain blood sugar levels.
Key Terms
glucose: a simple monosaccharide (sugar) with a molecular formula of C6H12O6; it is a principal source of energy for cellular metabolism
metabolism: the complete set of chemical reactions that occur in living cells
glycogen: a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria
glycogenolysis: the break down of glycogen into glucose
glycogenesis: the turning of glucose into glycogen