Assume that the binding of one molecule of epinephrine to a seven-transmembrane

Question

Assume that the binding of one molecule of epinephrine to a seven-transmembrane helix (7TM) receptor (also called the G protein-coupled receptor, or GPCR) results in the activation of 170 G? subunits. In addition, suppose that each activated adenylyl cyclase catalyzes the conversion of 20 ATP molecules to cAMP per second. (Assume that each G protein activates a single unique adenylyl cyclase.)

Calculate the number of moles of cAMP that are produced per second. Enter your answer to at least two significant figures.

Explanation / Answer

As per the given information,

Followed by epinephrine binding, Each G-protein activates single AC, each activated adenylate cyclase (AC) catalyses 20 ATP molecules to cAMP per sec.

170 subunits activate 170 AC molecules, and thus 170 * 20 ATP molecules to cAMP molecules.

i.e. total 3400 cAMP molecules are produced per sec.

Each mole contains 6.022x10^23 (Avagadro's number) number of cAMP.

So, 3,400 molecules are present in how many moles?

Number of moles of cAMP produced per sec = (3400) * (1 mol/ 6.022x10^23) * = 564.596 * 10^-23

In two significant figures it is, 5.6 * 10-21   moles.

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