What is a key structural difference between integral and peripheral membrane proteins?

• A. Peripheral proteins span the entire lipid bilayer, while integral proteins are found on the periphery.
• B. Peripheral proteins are embedded within the lipid bilayer, while integral proteins are loosely attached.
• C. Integral proteins are covalently attached to lipid groups, while peripheral proteins are not.
• D. Integral proteins span the entire lipid bilayer, while peripheral proteins are found on the periphery.

Answer: (D)