Proteins

• Proteins are interspersed throughout the cell-surface membrane, and are embedded in the phospholipid bilayer in two different ways.
• Some proteins exist within the phospholipid bilayer to provide mechanical support or to act as cell receptors for molecules such as hormones.
• Proteins possess several different functions within the cell-surface membrane, including structural support, allowing cell adhesion, acting as receptors, allowing active transport (carrier proteins) and permitting the transport of water-soluble substances (channel proteins).