endocrine 3 Flashcards
1.
what are gpcrs
common membrane receptors for lipid insoluble hormones
massive glycoproteins with hgih ligand specifity
what are gpcrs involved in
hormonal signalling
neurotrannsmitter signalling
emryonic development
sense reception
steps for gpcr reception
- hormone binds to gcpr
- conformational chnange is induced
- alpha subunit of g protein swaps gdp for gtp - gcpr and g protein are activated
- gprotein binds to enzyme
- gtp is hydrolysed to gdp by gtpase activity of alpha subunit
- energy activates the enzyme - usually adenylate cyclase
- deactivated g protein moves back to gcpr
why are lipid insoluble hormones called primary messengers
lipid insoluble hormones are complementary to receptors on th plb
do not bring a response directly
rely on a signalling cascade - often stimulated by binding to gcprs
what happens to gpcr when a hormone binds to it
causes a conformational change
the c.c activates g protein
g protein activaters adenylate cyclase which converts ATP to cAMP
cAMP acts as a secondary messenger
what does a secondary messenger do once activated
activate or inhibit enzymes
whats the role of cAMP
It activates protein kinases which transfer Pi to other molecules, e.g. ion channels
what is often the final molecule in the secondary messenger cascade
transcription factor
what do phosphodiesterases do
convert cAMP to AMP
STEPS OF SECONDARY MESSAGING
- Peptide hormones (first messengers) cannot pass the PLB so they bind to receptors in the membrane
- G-proteins are bound to receptors on the cytosolic side of the cell and binding activates them
- Activated G-proteins convert ATP to cyclic AMP (cAMP) which activates protein kinases; cAMP is the secondary messenger
- Kinases phosphorylate transcription factors which change the identity and proportion of gene products
how are steroid hormones carried in the bloodstream
by accessory proteins because they are water insoluble
how do steroid hormones move through the plb
dissue directly through
what do steroid hormones do after they diffuse inot the cell
bind intracellular recptors in the cytoplasm or nucleoplasm
when is mrna transcription altered
when hormone receptor complex binds to DNA
waht happens when the identity and abundance of proteins is altered
changes to cellular biochemistry brings about an appropriate response to initial stimulus
waht happens when hormone release stops
fewer hormone-receptor complexes are formed as set point is reached
thyroid hormone mechanism
- diffse directly acroos plb
- form hormone receptor complexes on mitochondira
- thyroid hormone receptor complexes will also bind to DNA
- ATP and mRNA production brings about cellular response to initial stimulus
how does hyperthyroidism cause tiredness
steroid hormones form hormone receptor complexes on mitochondira
leads to increased ATP production
decreases energy availibilty
= tiredness
steroid hormone steps overview
. Fatty-acid and cholesterol derived hormones can pass freely through the PLB
bind directly to receptors in cytoplasm to form hormone receptor complexes
steroid hormones bind to transcription factors which alter the production of gene products
