Extrinsic protein

An extrinsic protein is a protein around the whole cell membrane that has polar and nonpolar areas. Extrinsic proteins only partly span the membrane-they are either attached to the outer phospholipid layer or the inner phospholipid layer. They are held to the cell membrane by weak molecular attractions, like ionic, hydrogen, or Van der Waals bonds. Extrinsic proteins act as receptors, meaning they recognise and bind onto specific molecules, e.g. hormones.