Many G protein-coupled receptors contain seven transmembrane α-helical domains. 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 surface or on the cytosolic surface of the membrane. The loop on the cytosolic side between helices 5 and 6 is usually substantially longer than the others. Where would you expect to find the carboxyl end of the protein?
A) at the exterior surface
B) at the cytosolic surface
C) connected with the loop at H5 and H6
D) embedded in the phospholipid bilayer of the membrane

Question

Quizplus · Accepted Answer

Since the amino end of the protein is located at the exterior of the plasma membrane, it follows that the carboxyl end of the protein must be located at the cytosolic surface of the membrane, opposite to the amino end.

Many G Protein-Coupled Receptors Contain Seven Transmembrane α-Helical Domains