Pancreas & insulin Flashcards
Aantomy of pancreas & how it develoops!
Largest Gland in body!
develops embryologically as an outgrowth of the foregut
Describe the contents and structure of the pancreas
& functions of the pancreas
2 functions:
• ~ 1% endocrine tissue, 99% exocrine tissue
Exocrine: (acinar cells)
- produces digestive enzymes secreted directly into duodenum which forms the bulk of the gland
- Alkaline secretions through pancreatic duct into the duodenum
Endocrine: (Islets of Langerhans)
- hormone production
Describe what each endocrine cell of the pancreas secretes.
Delta “dogs”>> dont care about aplha or beta.. they inhibit humans in general (universal inhbitor of hormones) ;P
- Beta (β)-cells >> insulin
- Alpha (α)-cells >> Glucagon
- Delta (d)-cells >> somatostatin
- PP (pancreatic polypeptide) cells>> PP
- e cells>> Ghrelin
- G cells >> gastrin
- VIP (vasoactive intestinal peptide)
what do beta cells secrete?
• Major cell types in islets of langerhans?
How many disulphide bonds are present in a molecule of the hormone insulin?
3
Insulin structure (prcoess)
THe signal part “Pre” = ensures thes newly synthesizd protein enters the costernsl space of the ER
C-chain= connecting chain
insuling strucutre
(final)
polypeptide (A and B chains) interlinked by disulfide bonds!
- (additional intra-chain disulfide bond w/in the A chain)*
- Insulin is a big peptide with an alpha helix structure*
Synthesis of insulin (in the cell) and importance of C peptide
signal peptide is removed once it enter the ER, the remained prp-insulin folds and disulfide bonds form btw Cystine residues.
pro-insulin > Golgi & C-chain is cleaved off!
the final storage vesciles have equal amount of Cpeptides to insulin.
this makes the C peptide a good marker for measuring endogenous insulin release!
how is insulin stored?
it is stored in the B-cell storage granules as crystalline- ZINC insulin molecules!
how is insulin secreted?
glucose comes and attaches to GLUT 2 , it flips and glucose is released inside the cell (against its concentration gradient),
Glucose is converted to G-6-P by Glucokinase!, the phosphate group is so charged that it cannot pass through the membrane >> Glucose is now trapped!
More ATP produced from the metabolism of glucose results in inhibition of the ATP-sesnsitve potassium channels (KATP channels). >>Less positively charged potassium leaving the cell through K+ ATP channels results in depolarisation of the plasma membrane (i.e. makes the resting membrane potential less negative).
This depolarisation is sensed by voltage activated Ca+ channels which open allowing calcium to flow down its electrochemical gradient into the cell.
It is this influx of calcium ions into the β cell that activates the insulin containing vesicles causing them to fuse with the plasma membrane and release insulin.
what controls insulin secretion?
what stimulates its secretion?
what inhibits it?
actions of insulin
(favours storage)
1/2 life of insulin?
5 mins there is no carrier (cuz theyre water soluble)
insulin recepter strucutre!
tyrosine kinase
which cells have GLUT 2 transporters?
structure of Glucagon? secreted by what cells?
actions?
Alpha cells
opposite of INSULIN!
No disulphide bridges: =flexible structure
The major actions of glucagon are:
- Increase glycogenolysis and decrease glycogenesis in liver.
- Increase gluconeogenesis in liver.
- Increase ketogenesis in liver.
- Increase lipolysis in adipose tissue.
Mechanism of action of GLucagon (which recepter type)?
G-protein coupled recepter
just review
