The hydrophilic ends are in contact with water, while the hydrophobic ends face each other and do not touch the water. Membrane Proteins Integral and peripheral membrane proteins Floating in the phospholipid bilayer are many types of proteins. Marker proteins are like nametags that identify the cell to other cells. Each organism has its own unique marker proteins on its membranes. One of the functions of marker proteins is to enable a person's immune system to distinguish its cells from those of invading cells.
Active transport requires the use of energy.
They move materials in and out of the cell. Some of them function as pores that allow substances to diffuse through the membrane. Receptor proteins extend through the cell membrane. As the communication office of the cell, they allow the cell to interact with other cells. This causes the portion of the protein on the inside of the cell to change shape, triggering a reaction within the cell.