insulin/diabetes Flashcards
what is insulin produced by
islet of langerhans in pancreas
what are islet of Langerhans
cluster of endocrine cells scattered throughout the pancreas
what is insulin
small protein, peptide hormone, two peptide chains, stored as granules
structure of insulin
2 peptide chains
what synthesises insulin
beta cells as proinsulin
when is insulin released
as response to high blood glucose levels
other stimuli of insulin:
amino acids, fatty acids, parasympathetic nervous system, peptide hormones
what is insulin stored as
hexamers
what is a hexamer
3 dimers associating to form a hexamer stabilised by 2 zinc ions
what is a dimer
2 insulin molecules bonded by hydrogen bonds
what do hexamers precipitate to form and the effects of it
precipitates to form crystals, increases stability and protects against proteases
what is the process of insulin release
glucose enters beta cells
glucose metabolised
increase ATP/ADP intracellular ratio
K+ channels close
cell membrane depolarisation
voltage dependent Ca2+ channels open
Ca2+ influx
exocytosis of stored insulin
what is type 1 diabetes
no release of insulin
what is type 2 diabetes
early stages not enough is produced, later stages no response from cells
what is insulin inhibited by
low blood glucose and somatostatin
what is somatostatin
peptide hormone
what is somatostatin produced by
delta cells, hypothalamus, GIT
functions of insulin
promotes cell proliferation/tissue growth/development, promotes cell uptake of K+ and Ca2+, promotes uptake and storage of glucose/amino acids/fats after meals for fuel conservation
anabolic action of insulin
mainly on liver, muscle and adipocytes via insulin receptors to decrease glucose levels
what is anabolic action
mechanism of bonding smaller units together to make a bigger structure
what is an insulin receptor
tyrosine kinase receptor, preformed dimer
what are the relay proteins for insulin receptor called
IRS, insulin receptor substrate
how does glucose enter cells
transporters
what are glucose transporters
solute linked carriers of membrane transport