Metabolic Effects of Insulin and Glucagon

These flashcards cover key concepts regarding the metabolic effects of insulin and glucagon, their synthesis, actions, and the implications of their secretion on glucose metabolism.

What are the small peptide hormones that have a profound effect on energy metabolism?

Insulin and Glucagon.

Where is insulin produced in the body?

Insulin is produced by the β islet cells of the pancreas.

What is the main anabolic effect of insulin?

Insulin promotes glycogenesis, proteogenesis, and lipogenesis.

What is the structure of insulin?

Insulin consists of 51 amino acids in two polypeptide chains (A and B) connected by disulfide bonds.

What is the process of insulin synthesis?

Preproinsulin is converted to proinsulin, which is then cleaved to form insulin and C-peptide.

What triggers the exocytosis of insulin from β cells?

An increase in blood glucose levels triggers the exocytosis of insulin.

What physiological effects does insulin have on glucose metabolism?

Insulin promotes glucose uptake, glycogen synthesis, and inhibits gluconeogenesis and glycogenolysis.

What type of receptor does insulin bind to and what is its role?

Insulin binds to a transmembrane receptor that has tyrosine kinase activity, leading to various metabolic actions.

What role does glucagon play in glucose metabolism?

Glucagon opposes insulin, maintains blood glucose levels by promoting gluconeogenesis and glycogenolysis in the liver.

What stimuli lead to glucagon secretion?

Glucagon is secreted in response to hypoglycemia, low amino acids, and high levels of catecholamines.

What are catecholamines and how do they affect glucagon secretion?

Catecholamines, such as epinephrine, can stimulate glucagon secretion, especially under stress.

Describe the effects of glucagon on liver metabolism.

Glucagon increases liver glycogenolysis and gluconeogenesis and inhibits fatty acid synthesis.

What symptoms occur during hypoglycemia?

Adrenergic symptoms like anxiety, palpitation, and neuroglycopenic symptoms like confusion, headache.

What factors can lead to different types of hypoglycemia?

Insulin-induced, postprandial, and fasting hypoglycemia can occur due to varying physiological conditions.

What are the small peptide hormones that have a profound effect on energy metabolism?

Insulin and Glucagon.

Where is insulin produced in the body?

Insulin is produced by the \$\beta\$ islet cells of the pancreas.

What is the main anabolic effect of insulin?

Insulin promotes glycogenesis, proteogenesis, and lipogenesis.

What is the structure of insulin?

Insulin consists of 51 amino acids in two polypeptide chains (A and B) connected by disulfide bonds.

What is the process of insulin synthesis?

Preproinsulin is converted to proinsulin, which is then cleaved to form insulin and C-peptide.

What triggers the exocytosis of insulin from \$\beta\$ cells?

An increase in blood glucose levels triggers the exocytosis of insulin.

What physiological effects does insulin have on glucose metabolism?

Insulin promotes glucose uptake, glycogen synthesis, and inhibits gluconeogenesis and glycogenolysis.

What type of receptor does insulin bind to and what is its role?

Insulin binds to a transmembrane receptor that has tyrosine kinase activity, leading to various metabolic actions.

What role does glucagon play in glucose metabolism?

Glucagon opposes insulin, maintains blood glucose levels by promoting gluconeogenesis and glycogenolysis in the liver.

What stimuli lead to glucagon secretion?

Glucagon is secreted in response to hypoglycemia, low amino acids, and high levels of catecholamines.

What are catecholamines and how do they affect glucagon secretion?

Catecholamines, such as epinephrine, can stimulate glucagon secretion, especially under stress.

Describe the effects of glucagon on liver metabolism.

Glucagon increases liver glycogenolysis and gluconeogenesis and inhibits fatty acid synthesis.

What symptoms occur during hypoglycemia?

Adrenergic symptoms like anxiety, palpitation, and neuroglycopenic symptoms like confusion, headache.

What factors can lead to different types of hypoglycemia?

Insulin-induced, postprandial, and fasting hypoglycemia can occur due to varying physiological conditions.

What is the significance of C-peptide during insulin synthesis?

C-peptide is a byproduct of insulin synthesis, cleaved from proinsulin, and can be used as a marker for endogenous insulin secretion due to its longer half-life.

How does glucose enter pancreatic \$\beta\$ cells to stimulate insulin secretion?

Glucose enters \$\beta\$ cells primarily via the GLUT2 transporter, leading to ATP production, which in turn depolarizes the cell and triggers insulin release.

What is the mechanism of action for glucagon at its receptor?

Glucagon binds to a G-protein coupled receptor (GPCR) on target cells, which activates adenylate cyclase, increasing intracellular cAMP levels, and subsequently activating protein kinase A.

Beyond glucose, what are the general effects of insulin on lipid and protein metabolism?

Insulin stimulates lipogenesis (fat synthesis) and protein synthesis, while also inhibiting lipolysis (fat breakdown) and proteolysis (protein breakdown).

What are the primary target tissues where insulin promotes direct glucose uptake?

Insulin primarily promotes glucose uptake into muscle and adipose tissue by triggering the translocation of GLUT4 transporters to the cell membrane.