What is the name of the type of protein that is attached to the surface of the cell membrane bilayer?

The term for the type of protein that is attached to the surface of the cell membrane bilayer is "peripheral protein." These proteins are located on the outer or inner surface of the membrane and do not penetrate the lipid bilayer. Instead, they are usually associated with the membrane temporarily, often through interactions with integral proteins or with the phospholipid head groups. Peripheral proteins play significant roles in various cellular functions, including signaling pathways and maintaining the cell's shape.

Understanding the characteristics of peripheral proteins helps differentiate them from integral and transmembrane proteins, which span the membrane or are embedded within it, thereby playing different roles, such as acting as channels or transporters. Channel proteins specifically facilitate the passage of ions or molecules across the membrane, while transmembrane proteins extend across the entire membrane and can function as receptors, enzymes, or transporters.