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 380 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.

note- (Assume that 380 adenylate cyclase proteins are activated, and that each protein synthesizes 20 cAMP molecules. Calculate the total number of cAMP molecules produced per second by all the adenylyl cyclase, and then convert this number to moles per second using Avogadro's number (6.022 × 1023). The receptor is able to activate 380 G proteins, each of which is able to activate an adenylyl cyclase that converts 20 ATP molecules to 20 cAMP molecules. Assume that each G protein activates a unique adenylyl cyclase. Remember to convert molecules of cAMP to moles of cAMP.)

Explanation / Answer

1 molecule of epinephrine activates 380 G subunits.

1 G subunit activates 1 molecule of adenylyl cyclase.

1 molecule of adenylyl cyclase converts 20 molecules of ATP to cAMPsec.

Therefore,when 1 molecule of epinephrin will binds to GPCR,it will convert 380 X 20 molecules of ATP to cAMP

and this will be equal to 7600 molecules.

1 mole of a substance consists avogadros's number of molecules i.e 6.023 X 1023 molecules

7600 molecules = 7600 / 6.023 X 1023 moles  =1261.8 X 10-23 moles.

So, 1261.83 X 10-23 moles of cAMP are produced per second.

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