CELL BIOLOGY Essay Example | Topics and Well Written Essays - 500 words - 1

CELL BIOLOGY - Essay Example Cholera toxin alters the ÃŽ ± subunit such that the G protein becomes constitutively activated. The result is an increase in cAMP and associated kinases that would amplify the cascade effect and therefore enhance the effect of norepinephrine. If the weaker interaction is still sufficient to activate the receptor but also allows for a faster exchange rate for norepinephrine molecules, then the result would be to enhance the effect of norepinephrine. If, instead, the interaction was not sufficient to activate the receptor, then the effects of norepinephrine would be inhibited because the inactive receptor would not respond to the norepinephrine signal. This will likely inhibit the effects of norepinephrine, because although binding of norepinephrine will still activate the receptor at the same rate, the receptor would no longer be stably associated with the G protein, and the signal will not be transduced from activated receptor to inactive G protein as efficiently. If the ÃŽ ± subunit is responsible for activating adenylate cyclase and signaling an increase in cAMP and activation of resulting cAMP-dependent kinases, then altering the interaction between the ï  ¢Ã¯  § and the protein kinase will have no effect. If instead, the ï  ¢Ã¯  § - protein kinase interaction is necessary for amplification of the norepinephrine signal, then weakening the interaction will have the effect described above (i.e. it will depend on whether or not the weaker interaction is still sufficient to activate the kinase.) ⇒By inhibiting protein phosphatases in general, protein kinases—activated by phosphorylation— and their downstream targets will have longer half lives because phosphatases won’t be available to hydrolyze their phosphate groups. If these kinases and downstream targets are required to potentiate the norepinephrine signal, then the effects of norepinephrine would be enhanced. 2. Receipt of extracellular signals can cause changes in cellular physiology. Some changes