Plant cells are surrounded by a cell wall while animal cells do not have one. The cell wall is a rigid structure which encases the whole cell. It lies just outside the cell membrane. The thickness of the cell wall varies from one plant to another. The cell wall protects and supports the cell. It is made up mainly of cellulose and small amounts of pectin and lignin. The cell wall consists of many layers and when two cell meet, each one builds a part of the cell wall between them. In a way this is like a plaster wall that separates two rooms. The cell wall allows materials to pass through freely.