Endocrinology - Biochemistry Flashcards
what organ produces insulin
pancreas
what do each of the cells in the pancreatic islet do
alpha cells = secrete glucagon
beta cells = secrete insulin
delta cells = secrete somatostatin
PP cells = secrete pancreatic polypeptide
where is insulin synthesised in the beta cells
rough endoplasmic reticulum
how is insuli synthesised
preproinsulin –> proinsulin + signal peptide –> insulin + c-peptide
what is the structure of insulin
two polypeptide chains linked by disulphide bonds
what is the function of C peptide
no biological or physiological function - is secreted alongside the insulin
ultra-fast/ulate short acting insulin preparation
lispro
short-acting insulin preparation
regular
intermediate acting insulin preparation
NPH/lente
long acting insulin preparation
ultralente
ulta-long acting insulin preparation
glargine
how are the different insulin preparations mad
by changing the order of amino acids slightly
describe the structure of ultrafast/ultra short acting insulin
monomeric
non antigenic
very fast acting (15mins)
how is the ultrafast/ultra short acting insulin administered
alongside a longer acting insulin
IV infusion - on its own
how is insulin secreted
glucose enters B cells (GLUT2 transport) and is phosphorylated by glukokinase
increaed glucose metabolism therefore increase in ATP
ATP inhibits KATP channels
this depolarises the cell
this means Ca voltage gated channels open allowing an influx of Ca into the cell
secretory vesicles fuse with the membrane to release insulin
