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p17  Cell Membrane Versus Cell Wall

Cell Wall
The cell wall is a rigid layer of nonliving material that surrounds the cells of plants and some other organisms. The cells of animals, in contrast, do not have cell walls.
The cells of animals, in contrast, do not have cell walls.A plant’s cell wall helps to protect and support the cell. The cell wall is made mostly of a strong material called cellulose. Although the cell wall is tough, many materials, including water and oxygen, can pass through easily.

Cell Membrane
All cells have cell membranes. In cells with cell walls, the cell membrane is located just inside the cell wall. In other cells, the cell membrane forms the outside boundary that separates the cell from its environment.


The cell membrane controls what substances come into and out of a cell.

The cell membrane controls what substances come into and out of a cell.
Everything the cell needs, from food to oxygen, enters the cell through the cell membrane. Fortunately, your ship can slip through, too. Harmful waste products leave the cell through the cell membrane. For a cell to survive, the cell membrane must allow these materials to pass in and out. In addition, the cell membrane prevents harmful materials from entering the cell. In a sense, the cell membrane is like a window screen.
In a sense, the cell membrane is like a window screen. The screen allows air to enter and leave a room, but it keeps insects out.