Which type of membrane protein is loosely bound to the surface of the membrane?

Peripheral proteins are located on the surface of the cell membrane and are loosely bound to it. Unlike integral proteins, which span the membrane and are embedded within the lipid bilayer, peripheral proteins do not penetrate the hydrophobic core. They interact with the membrane primarily through non-covalent interactions, such as ionic bonds and hydrogen bonds, with polar heads of phospholipids or with integral proteins. This allows them to play various roles in cellular processes, such as signaling and maintaining the cell's shape, without being tightly interwoven into the membrane itself.

In contrast, channel proteins create pathways for ions and molecules to cross the membrane; integral proteins are embedded within the membrane structure; and transport proteins facilitate the movement of substances across the membrane but are also typically integral proteins. The unique positioning of peripheral proteins on the surface underlines their role and functions distinct from the other types of membrane proteins.