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Glycogenolysis is regulated hormonally in response to blood sugar levels by glucagon and insulin, and stimulated by epinephrine during the fight-or-flight response. Insulin potently inhibits glycogenolysis.
This process is called glycogenolysis. Liver cells, or hepatocytes, have glucagon receptors which allow for glucagon to attach to them and thus stimulate glycogenolysis. [13] Contrary to insulin, which is produced by pancreatic β-cells, glucagon is produced by pancreatic α-cells. [14]
The flat line is the optimal blood sugar level (i.e. the homeostatic set point). Blood sugar levels are balanced by the tug-of-war between 2 functionally opposite hormones, glucagon and insulin. Blood sugar levels are regulated by negative feedback in order to keep the body in balance.
Beta cells are sensitive to blood sugar levels so that they secrete insulin into the blood in response to high level of glucose, and inhibit secretion of insulin when glucose levels are low. [10] Insulin production is also regulated by glucose: high glucose promotes insulin production while low glucose levels lead to lower production. [11 ...
Glucagon is a protein hormone that blocks the effect of insulin on hepatocytes, inducing glycogenolysis, gluconeogenesis, and reduced glucokinase activity in hepatocytes. The degree to which glucose suppression of glucagon is a direct effect of glucose via glucokinase in α cells, or an indirect effect mediated by insulin or other signals from ...
Conversely, glycogenesis is enhanced and glycogenolysis inhibited when there are high levels of insulin in the blood. [15] The level of circulatory glucose (known informally as "blood sugar"), as well as the detection of nutrients in the Duodenum is the most important factor determining the amount of glucagon or insulin produced.
Glycogen phosphorylase catalyzes the rate-limiting step in glycogenolysis in animals by releasing glucose-1-phosphate from the terminal alpha-1,4-glycosidic bond. Glycogen phosphorylase is also studied as a model protein regulated by both reversible phosphorylation and allosteric effects.
Glucagon causes the liver to engage in glycogenolysis: converting stored glycogen into glucose, which is released into the bloodstream. [3] High blood-glucose levels, on the other hand, stimulate the release of insulin. Insulin allows glucose to be taken up and used by insulin-dependent tissues.