Question

what cells do insulin and glucagon act on? and what does insulin/glucagon signaling promote/lower in these

cells?

Answer 1

Insulin and glucagon are hormones secreted by islet cells within the pancreas. They are both secreted in response to blood sugar levels but in opposite fashion! Insulin is normally secreted by the beta cells (a type of islet cell) of the pancreas and glucagon is secreted by alpha cells in the islets of Langerhans of the pancreas. Insulin has multiple actions in each of these tissues, the net result of which is fuel storage (glycogen or fat). Glucose enters the circulation either from the diet or from the synthesis in the liver.

the liver, muscle, and fat have been regarded as major target tissues for insulin. In contrast, Liver cells have glucagon receptors. When glucagon binds to the glucagon receptors, the liver cells convert the glycogen into individual glucose molecules and release them into the bloodstream, in a process known as glycogenolysis.