A major group of G protein-coupled receptors contains seven transmembrane α helices. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others.
Where would you expect to find the carboxyl end?
a. at the cytosol surface
b. connected with the loop at H5 and H6
c. between the membrane layers
d. at the exterior surface

a. At the cytosol surface

Explanation:

The G protein coupled receptors have seven transmembrane alpha helices and because of this they are able to pass through the cell membrane seven times.Like every protein, this receptor also has to terminals - one is the N-terminus and the other is the C-terminus.The N-terminus is the amino end of the receptor whereas the C-terminus is the carboxyl end of the receptor.The N-terminus lies on the extracellular side and then it crosses the membrane 7 times such that the C-terminus faces the inside that is towards the cytosol.The fact that the loop on the cytosol side between helices 5 and 6 helps us to know that the 7th loop must go outside and by coming back in the C-terminus would eventually face the cytosol.