Cell Signalling and the Endocrine System Flashcards
what is the function of a ligand-gated ion channel
when activated, by binding of a ligand/hormone, they will allow movement of ions in or out of the cell
(ie depolarisation or hyperpolarisation of plasma membrane)
(occurs in milliseconds)
in what direction do ions move through a ligand-gated ion channel
down the conc. gradient, ie from area of higher charge to lower
what types of endocrine receptors are membrane-bound
ligand-gated ion channels, G-protein coupled receptors(GPCR), Kinase-linked receptors
describe the general mechanism of a G-protein coupled receptor(GPCR)
agonist(eg hormone) binds to receptor bringing conformation change of GPCR which allows activation of signalling response
give an example of a hormone and a GPCR in the endocrine system
adrenaline, binds to B2 adrenoreceptor which is a GPCR, activates signalling response of enzyme to convert ATP to cAMP, and ultimately results in bronchodilation
(occurs in seconds)
describe how the action of a GPCR ends
ends when GTP bound to the alpha-subunit hydrolyses to become GDP, so self-limits the action
what happens when the agonist/hormone dissociates from the GPCR
resets confirmation of GPCR, subunits return to original positions, ready to receive another agonist and repeat process
what is an adrenoreceptor
a receptor bound and activated by the neurotransmitters/hormones adrenaline and noradrenaline
what is the principal transduction of the a1 adrenoceptor(it is a GPCR)
Galpha-subunit q, activates phospholipase, which increase IP3 and DAG
what is the principal transduction of the a2 adrenoceptor
Galpha-subunit i, inhibits adenylyl cyclase, decreasing cAMP and Ca2+ channels, increasing K+ channels
what is the principal transduction of the B1, B2 and B3 adrenoceptors
Galpha-subunit s, stimulation of adenylyl cyclase, increasing cAMP
give an example of a hormone that is an agonist for Kinase-linked receptors
insulin
describe what happens when a hormone/agonist binds to a Kinase-linked receptors
dimerisation of receptor, with subsequent phosphorylation by ATP of tyrosine residues linked to receptor
what binds to the phosphorylated tyrosine residues in a Kinase-linked receptor action
relay proteins
describe the signalling response of a Kinase-linked receptor
diversified, different relay proteins bind to the tyrosine residues and illicit varied cellular responses
(response occurs in hours)