Lecture 2 - Insulin and Friends Flashcards
what can goldfish convert lactate into
ethanol
insulin is synthesised as a pre-pro-peptide, what is this
small protein
what is the pre sequence in insulin responsible for
the export from the cytosol of the cell
- in this case to secretory granules
what does the pro-sequence of insulin seem to be important for (and what happens to it)
proper folding of insulin and it is removed
what bonds and structure interactions does insulin have
disulfide bonds (C-C) as well as secondary and tertiary structure interactions (covalent linkages)
where is insulin made
made in the islets of Langerhans in the pancreas (B cells)
what do alpha cells in the pancreas produce
glucagon
what are two of the endocrine hormones produced in the pancreas
insulin and glucagon
insulin typically forms hexamers with what in B cells and what does this mean
Zn = causes insulin to be packed very tightly together and held into hexamers
insulin forms what in the blood
monomers in blood
circulating insulin interacts with what
receptors on some tissues (fat, muscle and liver etc)
the insulin receptor is synthesised as one protein and then what happens for its full function form (what does it form)
it is cleaved (modified) for full function (forms a dimer)
what gives rise to different insulin receptor isoforms
splicing variants during mRNA processing
how many splices is the insulin receptor split into
3
where does the largest splice (A chain) of the insulin receptor sit
sits outside the cell and folds
where does the B chain of the insulin receptor sit
the first part of B chain is in the membrane, other part is inside the cell
insulin is a what on the surface of the cell
dimer
what are the three domains of the insulin receptor
- extracellular domain
- transcellular domain
- cytosolic domain
what will activate the insulin receptor
insulin binding
when there is no ligand (insulin) present at the receptor what does the receptor do
remains inactive
what does binding of insulin cause to the receptor
structural changes and activates the receptor
specifically what part of the receptor is changes when insulin binds
tyrosine kinase domain
in a normal body insulin is released from where and in response to what
insulin is released from B cells in response to blood glucose
in a normal body when the insulin receptor is stimulated what happens
receptor is stimulated, GLUT4 moves to the cell surface to transport glucose
glucose is taken up by the cell
what is the problem with insulin in type 1 diabetics and what is the cause of this
no functional insulin, autoimmune disease or variant insulin
what is the problem with insulin in type 2 diabetics and what is the cause of this
reduced receptor sensitivity, obesity or rare genetic receptor variants
(receptor not responding to insulin)
what does the uptake of glucose stimulate
oxidative metabolism and ATP production
increased metabolic activity stimulates the conversion of what and the release of insulin
conversion of proinsulin and release of insulin
what is the function of GLUT4 and where is it found
insulin-dependent glucose uptake, found in striated muscle and adipose tissue
what is the broad process called that GLUT4 does
endo and exocytosis
what is the function of GLUT2 and where is it found
largely responsible for insulin-independent uptake of glucose (it happens on its own)
found in kidney, liver, pancreatic B cells, basolateral membrane of small intestine
what is endocytosis
internalising molecules, particles, or fluids from the external environment by engulfing them into membrane-bound vesicles
what is exocytosis
cells release molecules, particles, or fluids from internal vesicles into the extracellular environment
