here's the first summary that i tried this semester:
this lecture introduces the concept of metabotropic transmission, which is essentially when membrane receptor proteins set off chains of reactions of proteins and enzymes which then mediate a cell response which is generally longer lasting, more amplified than that of ionotropic receptors. g proteins are the single most important transducer molecule in that they are the first intermediate which set off the chain reactions. they are energized by GTP and can affect ion channel permeability, create second messengers, and regulate protein transcription.
second messengers are then detailed, with an emphasis on cAMP, its synthesis and its actions. cAMP is synthesized when g proteins stimulate adenyl cyclate to make cAMP from ATP. the total cAMP in the cell is a summation of the stimulatory and inhibitory activity of g-proteins. cAMP then stimulates enzyme protein kinases, which then can have a plethora of effects on the cell. specific examples: affect excitability of cell by affecting permeability of non gated K+ channels. convert glycogen to glucose in the liver. release fatty acids from adipose cells. etc. etc.
the other two second messengers talked about in this lecture are IP3 and DAG. the synthesis pathway is: g proteins stimulate PLC to cleave PIP into IP3 and DAG. IP3 is responsible for Ca+ release in smooth muscle cells and DAG is responsible for cell growth and proliferation.
the last main concept in this lecture is the regulation of gene transcription and ion channel permeability (up and down regulation) by g-proteins. the former is accomplished by protein kinases stimulating CREB, which is a translational activator. the latter is accomplished by cAMP stimulating protein kinases to interact with transcription factors which then produce proteins that interact with the protein channels on a long term basis (contrast this with the way that g proteins sometimes directly bind to ion channels)
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