Summary
Glycogenesis stores glucose as glycogen and glycogenolysis breaks it down when energy is needed.
In depth
Glycogen synthase and branching enzyme build glycogen; phosphorylase releases glucose-1-phosphate. Liver glycogen maintains blood glucose (about 100 g), muscle glycogen fuels muscle only. Adrenaline and glucagon activate breakdown via cAMP.
Glycogen allows quick glucose release. Regulation by phosphorylation: adrenaline activates breakdown, insulin promotes synthesis. Muscle lacks glucose-6-phosphatase, so can't release glucose to blood.
Example: runners 'hit the wall' when glycogen runs out.
Glycogen is a branched polymer of glucose stored mainly in liver (about 100 g) and muscle (about 400 g). Glycogenesis, stimulated by insulin, uses glycogen synthase to add glucose from UDP-glucose; glycogenolysis, stimulated by glucagon and adrenaline, uses glycogen phosphorylase to release glucose-1-phosphate.
Liver glycogen is converted to free glucose by glucose-6-phosphatase and released to maintain blood sugar; muscle lacks this enzyme, so its glycogen only fuels the muscle itself. Many branch ends allow rapid mobilisation. Hormone signals use cascades of cAMP and protein kinase A, which amplify the signal.
Example: marathon runners hit the wall when glycogen runs out.
Remember: glycogen storage diseases, such as McArdle disease, arise from enzyme defects.
Frequently asked questions
What is Glycogen Metabolism?
Glycogenesis stores glucose as glycogen and glycogenolysis breaks it down when energy is needed.
Which area of biology covers Glycogen Metabolism, and how advanced is it?
Glycogen Metabolism is one of the 53 topics in Metabolism & Bioenergetics. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Hormonal Control of Metabolism, Anabolism and Catabolism, Gluconeogenesis.
Can you give an example of Glycogen Metabolism?
Glycogen storage diseases such as McArdle's lack muscle phosphorylase.
What should I learn before Glycogen Metabolism?
Work through the Beginner topics in Metabolism & Bioenergetics first, such as Metabolism, Anabolism and Catabolism, ATP, then return to Glycogen Metabolism. Intermediate topics assume the Beginner vocabulary.
What topics are related to Glycogen Metabolism?
The closest topics to Glycogen Metabolism are Hormonal Control of Metabolism, Anabolism and Catabolism, Gluconeogenesis, Glucose as Fuel. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Glycogen Metabolism?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Glycogen Metabolism. To practise the whole of Metabolism & Bioenergetics, use the Metabolism & Bioenergetics quiz.
How is Glycogen Metabolism different from Hormonal Control of Metabolism?
Glycogen Metabolism: Glycogenesis stores glucose as glycogen and glycogenolysis breaks it down when energy is needed. Hormonal Control of Metabolism: Insulin, glucagon, cortisol, adrenaline and thyroid hormone coordinate fuel use across tissues. Read both side by side and note what each one explains.
How should I study Glycogen Metabolism step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Hormonal Control of Metabolism and explain the difference aloud. Finally, take the Metabolism & Bioenergetics quiz and come back to this page for any question you miss.