Functions of The Cell Membrane!

The purpose of the membrane is to control what goes in and out of the cell. The items that go in are highly regulated. It also communicates with other cells for example with receptors on the surface or cell to cell union. Proteins that are found in the bilayer are receptor proteins, which deal with communication, recognition proteins and transport proteins that regulate the movement of water and soluble molecules through the membrane. In order to regulate the transport of molecules, there are two types of proteins in the cell: carrier proteins and transport proteins. The two types of transport proteins are channel and carrier protein. Transport is either active or passive. Active transport is moving molecules against the concentration gradient and energy is required in the form of ATP. Passive transport is moving molecules down the concentration gradient and no energy is required. Examples of passive transport are diffusion, which moves from high concentration to low concentration and osmosis, which is the diffusion of water molecules. Finally, the cell membrane is important for the connections between cells. There are four different types of these connections. Desmosomes attach cells together like "glue". A tight junction consists of fusing the cells together. A gap junction consists of pairs of channels fused. Finally, plasmodesma consists of binding plants together.