Intracell Signal (2)-effector Mechanism Flashcards
What can effectors be?
Enzymes -eg Adenyl cyclase
Ion channels
Voltage-operated Ca2+ channels
G-Protein regulated inwardly-rectifying K+ channels
Describe the agonist stimulated regulation of adenyl cyclase on a G(s) receptor
Agonist binds to G-protein coupled receptor which stimulates the change of a-GDP to a-GTP. This subunit then stimulates adenyl cyclase, which turns ATP to cAMP. The cAMP is then used as a 2ndry messenger to cyclic AMP-dependant protein kinase (PKA)
Describe the agonist-stimulated regulation of adenyl cyclase on a G(i) receptor.
Agonist binds to receptor, this changes the a-GDP subunit for a-GTP. This then inhibits the adenyl-cyclase enzyme and so ATP is not converted to cAMP. The cyclic AMP-dependant protein kinase doesn’t get activated. There is no second messenger
Describe the structure of cyclic AMP dependant protein kinase and how this relates to structure?
2 regulatory subunits- this is where cAMP binds
2 catalytic units - these are released once the cAMP has bound and go on to perform their function.
Their function is to phosphorylate target proteins in the cell (stimulate or inhibitory effect)
Describe the agonist-stimulated regulation of phospholipase C, using G(q) receptor.
The agonist binds to the receptor turning A-GDP to a-GTP. This then acts upon the phospholipase C enzyme which hydrolyses PIP2 to IP3 and DAG. IP3 binds to a receptor on the ER which opens the gate and allows more Ca2+ out into the cytoplasm . These Ca2+ can then bind to protein kinase A with the DAG.
Describe the signal pathway of Inotropy in the heart.
Adrenaline/noradrenaline bind to B-adrenoreceptor, this turns a-GDP to a-GTP. This then activates adenyl cyclase enzyme which turns ATP to cAMP. This activates the cAMP-dependant protein kinase. This in turn goes on to phosphorylate the voltage-operated calcium channel, so that the next time it is depolarised more Ca2+ is released and contractility increases.
How does smooth mulch have increased contraction?
In vascular smooth muscle noradrenaline interacts with a1-adrenoreceptors to vasoconstrictor.
In bronchiole smooth muscle, Acetylcholine reacts wit M3-muscurinic receptor to cause bronchi constriction.
Describe the signal pathway in the modulation of neurotransmitter release.
Morphine binds to mew-opioid receptor. This turns a-GTP to a-GDP and releases B/y subunit. The B/y subunit binds to the voltage-operated Calcium Chanel. This means that on its next depolarisation less Ca2+ is include and so less neurtotramitter is released and therefore pain is reduced as less AP’s form.
Key=uses B/y subunit not a-GTP as other mechanisms
What are some key features of bio signalling pathways?
Diversity - range of stimulant, receptor, G-protein and effector
Specificity-of ligand-receptor and subunits and effectors
Amplification-allows small change in extracellular signal to provide significant change in cell behaviour.
