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

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 230 Ga subunits. In addition, suppose that each activated adenylyl cyclase catalyzes the conversion of 30 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.

--Note that these numbers are used for illustrative purposes only. The actual rates are different (and larger), and vary depending on type of receptor and regulatory proteins that increase or decrease the rate of the GTPase activity of the G? subunit.

Explanation / Answer

260 x 20 = 5200 molecules / sec

(5200 molecules / sec) x (1 mol/ 6.022x1023) = 8.638x10-21 moles / s

rounded to 2 sig figs: 8.6x10-21

Hope this helps.

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