The cell wall is a rigid structure outside of the cell membrane composed mainly of the polysaccharide cellulose . As pictured at left, the cell wall gives the plant cell a defined shape which helps support individual parts of plants. In addition to the cell wall, plant cells contain an organelle called the chloroplast . The chloroplast allow plants to harvest energy from sunlight. In this way, plant cells manufacture glucose and other carbohydrates that they can store for later use.
Organisms contain many different types of cells that perform many different functions.
In the next lesson, we will examine how individual cells come together to form larger structures in the human body.