Final answer:
Peripheral proteins are not embedded in the plasma membrane; they are associated with its surface. The plasma membrane includes integral proteins, cholesterol, and phospholipids. Option B is correct.
Step-by-step explanation:
The correct answer to the question of what is not included in the plasma membrane is peripheral proteins. The plasma membrane is primarily composed of a phospholipid bilayer, with embedded cholesterol and integral proteins.
Cholesterol provides flexibility to the plasma membrane, integral proteins can serve as channels or pumps to move materials across the membrane, and phospholipids form the primary structure of the bilayer. However, peripheral proteins are not embedded within the plasma membrane but rather are associated with its surface, either attached to integral proteins or to the phospholipid heads.
The plasma membrane includes all of the following except:
integral proteins
peripheral proteins
cholesterol
phospholipid