Glycogen Metabolism and Energy Production

Study Notes

Glucose is a six-carbon molecule used to make energy in the form of ATP.
Glucose is stored in the body as glycogen, a large molecule made up of glucose units linked together.
Glycogen is compact and capable of rapid addition and removal of glucose units due to its branching structure.
After consuming a meal, glucose is absorbed into the bloodstream, causing blood sugar to rise.
The pancreas responds to high blood sugar by secreting insulin, which signals cells to absorb more glucose and convert it to glucose-6-phosphate.
Glucose-6-phosphate is then broken down during glycolysis, producing ATP as a byproduct.
Over time, as ATP levels rise, certain enzymes in glycolysis are inhibited, allowing excess glucose-6-phosphate to be used to make glycogen.
Glycogen synthesis involves the formation of a short linear glycogen chain as a primer, which is then elongated and branched through the addition of more glucose units.
During fasting or low-energy states, the body breaks down glycogen to release individual glucose units back into the bloodstream for use as energy.
The breakdown of glycogen involves the cleavage of alpha-1-4 bonds and the transfer of phosphate groups to released glucose units.
The liver and muscle cells have different enzymes to regulate glycogen metabolism, leading to different outcomes in each tissue.
Insulin and glucagon are the primary hormones that regulate glycogen metabolism, with insulin promoting synthesis and glucagon promoting breakdown.