The cell membrane is the barrier between a cell and its environment. Some cells also have a cell wall, which provides further protection and some support for the cell.
Animal cells are enclosed by a cell membrane, which is also called a plasma membrane. The cell membrane is formed from proteins with enough lipids to allow some flexibility. Some of the proteins in the cell wall allow transport for nutrients for the cell and the removal of waste products. Plants, fungi, bacteria and algae are surrounded by a cell wall in addition to the cell membrane. The cell wall is rigid for support, and it contains chemicals that help cells adhere together.