Cell Structure and Function

What Are the Differences between Plant and Animal Cells?

Plant and Animal Cells

Plants and animals are both composed of eukaryotic cells, but their cellular structures differ in important ways. Plant cells have cell walls, while animal cells do not. The plant cellglossary term (opens in a new window) wall is made of celluloseglossary term (opens in a new window). The cellulose is organized in a matrix comprising a tough outer layer that supports the plant and allows pressure from liquid to build up inside the cell. The cell wall also provides protection against mechanical damage. Small holes in the cell wall allow materials to enter and to leave the cell. The cell wall makes plant cells rigid, preventing free movement of the cell within plant tissue. In contrast, many animal cells can move freely within an organism.

Chloroplasts are found in most plant cells and in some protists but not in animal cells. Chloroplasts allow plants and certain protists to make their own food through photosynthesis. During photosynthesis, chloroplasts use the energy in sunlight to drive a chemical reaction between carbon dioxide and water. This chemical reaction produces oxygen and sugars. The sugars serve as food for the plant.

Plant and animal cells differ in the size and function of their vacuoles. Plant cells typically have a single, large vacuole, while some protists and animal cells have smaller, often multiple, vacuoles. In both plant and animal cells, vacuoles store nutrients and waste. Vacuoles in plant cells have the additional function of maintaining pressure against the cell wall. This pressure helps keep the plant upright. The amount of water available to the plant affects the degree to which vacuoles maintain pressure. A shortage of water causes vacuoles to shrink. This, in turn, causes the plant to wilt. When more water becomes available, vacuoles expand and the plant stands upright again.