General MEH Flashcards
Where in the pancreas and in what cells are insulin and glucagon produced?
Islets of Langerhans
Alpha cells - glucagon
Beta cells - insulin
How many polypeptides is insulin and how many disulphide bonds are there?
2 polypeptide chains
3 disulphide bonds
What is the name of the protein that is cleaved from the middle of the insulin polypeptide to create 2 chains? What is its clinical significance?
C-peptide
C-peptide is released into the blood in equimolar amounts with mature insulin, so measurement of C-peptide is a good indication of endogenous insulin synthesis in the body.
What amino acids do disulphide bonds form between?
Form between 2 thiol groups of cysteine residues.
Which receptors does insulin bind to?
Tyrosine-kinase receptors
Which receptors does glucagon bind to?
GPCRs (Gs)
How is insulin stored in Beta cells in the pancreas?
Stored as crystalline zinc-insulin complex
What are the 3 main tissues in the body that insulin acts on?
Liver, skeletal muscle and adipose tissue (as well as being required for normal growth and development of most tissues).
Out of insulin and glucagon, which is anabolic and which is catabolic?
Insulin - anabolic
Glucagon - catabolic
What is diabetic ketoacidosis?
Lack of insulin body increases lipolysis, and fatty acids are converted to ketone bodies in a process called beta oxidation. The ketone bodies create a metabolic acidosis in the body (bicarbonate system tries to buffer this but eventually can’t) - creates life-threatening condition.
What is the triad of symptoms of diabetes? What causes each symptom?
Polyuria - excess glucose in kidney, not all of it can be reabsorbed, increases water loss.
Polydipsia - excess thirst due to water loss.
Weight loss - loss of insulin leads to unopposed glucagon and catabolic effects in the body.
Name some symptoms of diabetic ketoacidosis.
Vomiting Nausea Abdominal pain Hyperventilation (to try to compensate for metabolic acidosis) Dehydration
What are the glucose concentrations that would indicate a diagnosis of diabetes?
Venous plasma glucose concentration > 11.1mmol/L
Fasting plasma glucose concentration > 7mmol/L
Plasma glucose concentration > 11.1mmol/L 2 hours after 75g anhydrous glucose in an oral glucose tolerance test.
What does the drug metformin do?
Reduces gluconeogenesis.
What do sulphonylureas do?
Increase insulin release from remaining beta cells, and reduce insulin resistance.
