Question

Acetylcholine binds to a G-coupled protein receptor on the heart muscle to make the heart beat more slowly. It does so by stimulating the opening of K+ channels in the plasma membrane, which makes it more difficult to initiate and action potential. Describe the following on contraction of the heart.
A.) Addition of a drug that inhibits the GTPase activity of the Ga subunit.

B.) Mutations in the K+ channel that keep it closed all the tiem.

C.) A mutation that decreases the affinity of the (Beta gamma) complex of the G protein for the K+ channel.

Answer 1

A) Addition of a drug that inhibits the GTPase activity of the Ga subunit:

This condition decreases the affects of acetylcholine, so increases the heart rate.

B) Mutations in the K+ channel that keep it closed all the time:

This condition also decreases the affects of acetylcholine, so it increases the heart rate.

C) A mutation that decreases the affinity of the (Beta gamma) complex of the G protein for the K+ channel:

This condition also decreases the affects of acetylcholine, so that it increases the heart rate.