Biologists use the fluid mosaic model to describe the composition of cell membranes and the role membranes play within living things.
what are the major components of cell membranes?
describe function of cell membranes & each component that make up the membrane.

The cell membrane can best be imagined as the gated community of a cell. it controls the flow of substance inside and out of the cell as well separate it from its external environment.
its major components are a phospholipid bilayer which acts as a semi permeable membrane separating the cell from its surrounding and providing a gradient for diffusion and osmosis.
proteins which act as gates and channels for the transport of macro  molecules into and out of the cell as well provide energy for facilitated diffusion or active transport via atp bound proteins.