The cell membrane protects the inside of the cell from the outside world.
The cell wall protects the plants inside of the cell from the outside world.
<span>A substance<span> is a pure form of matter that contains only one type of atom or molecule. It can be further divided into two sub-categories: elements and compounds.</span> The types of substances that most readily diffuse through a cell membrane, however, are the nonpolar and small <span>polar molecules like carbon dioxide and <span>oxygen. These two </span>molecules<span> simple diffusion of water through the membrane thru a process known as osmosis.</span></span></span>
