14. Hormone Regulation and Action Flashcards
What are three important res of calcium in cells?
- signal transductin pathways- acts as a second messenger
- neurtransmitter release
- contraction of muscle cells
- enymes that require calcium ions as a cofactor
- extraceuar maintains ptential difference across cell membranes
- bone formation
how are horones recognised?
a hormone molecule has a specific shape that is recognised by the hormones receptor
what are the three processes of signalling by hormones?
- Reception - binding of homrne (signal molecule or ligand) to its receptor - causes change and interacts with other proteins
- signal transduction intracelluar signals occur
- celluar response trigger a celluar response
what are three features of membrane permeable hormones
- they are lipid soluable (lipophilic) but they dont like water
- they can diffuse across the membrane of cells
- transported in the blood stream after binding to receptor proteins
- dissociate fro binding proteins before entering the target cell
where are steroid recpeptors located and how are they classified?
usually intracelluar (because steroid hormones are mebrane permeable) and they are classified according to their celluar location, their dimersation and the sequences of DNA they bind too
what happens to the nuclear receptor when there is a binded ligand? (genetic interaction)
- ligand binded domain closes
- inhibitory proteins dissociate
- binds to DNA which allows gene transcription
what horomones stimulate the nuclear receptor? (4) - the superfamily of membrane permeable hormones
steroid, thyrid, reinoids, vitamin D
what is the result of a non-genomic action of a steroid hormone (4 points)
opening of ion channels
activate classical second messenger systens
dont require gene transcription and translation! (protein synthesis)
requires the continued release of the hormone
what are three classes of cell- surface receptors for membrane IMPEREABLE hormones?
what are they made of?
- G-proteins coupled receptors
- enyme-linked receptors
- ion channel-linked receptors
they are made of proteins and peptides which are water soluable and dont diffuse through the lipid membrane!!!
what is the structure and function of G-protein coupled receptors?
structure: seven-transmembrane domain receptors
function:
- sense molecules outside the cell
- activate signal transduction pathways inside the cell
- then activate celluar response
they are like molecular switches!!
how do G-proteins function as a molecular switch?
when GTP is bound (guanosine triphosphate) its on
when GDP is bound (guansine diphosphate) its off
what is GTP? (guananine triphosphate) and how does it become GDP? (guanonine diphosphate)
- GTP is a source of energy for protein synthesis. (activates)
- necessary for signal transduction, particuary with G-proteins (it binds to them) as a second messenger
it become GDP by phophorylisation after GTPase hydrolyses GTP and it switches it off (GDP= inactive
cyclic AMP do to protein kinase A?
cAMP acts as a second messenger to activate protein kinase A!
when there is an inactive kinase A, it has a reguatory subunit that requires phosphorylisation. when cAMP comes a long, it phosphorlyates protein kinase A and and activates it to create a celluar response!!!
look at image
how does phospholipase C create second messengers?
phosphipase C hydrolyses a membrane phospholipidd PIP2 to geneate two second messenger - IP3 and DAG
IP3 releases calcium fro the ER
what happens when receptors are directly linked to an enyme? three steps
- a signal molecule attaches to the enyme on the extracelluar side
- the signal molecue activates the enzyme which causes dimerisation
- ATP –> ADP causes phosphorylisation and relay proteins to join
- celluar response
how do ligand gated ion channe receptors function?
ligand-gated ion chanels are transmembrane ion channels which open to allow ions through in resonse to the binding of a ligand (hormone - eg a neurotransmitter)
presynaptic–> postsynaptic
what is a signal transduction pathway?
when there is reception, transduction and celluar response.
- in most cases, the original signalling molecule (hormone) dosent enter the cell, it sends a cascade of phosphoryaisatin and dephosphorilsation intracelluary to get a celluar response
how do different responses from the same hormone occur?
- because there can be the same extracelluar signal molecule, but a different cell (so the intracelluar reaction will be different as the signal molecule, ie hormone, dosent enter the cell)
- dependant on the receptor proteins inside the cell
give an example of a hormone that has different effects on different cells
epinehrine (adrenaline) -
alpha receptor - blood vessels constricts
- beta receptor- skeletal blood vesse opens wider
- break down of glycogen in liver quickly
