Peroxisomes are a type of organelle, small structures found inside cells that carry out many of the important jobs in the cell. They are found not only in animal cells but in plant cells as well.
Peroxisomes range from 1/2 micrometer to 1 1/2 micrometers in diameter and contain a variety of enzymes, proteins that can catalyze reactions. A single membrane encloses their contents.
In plants, just as in animals, peroxisomes break down toxic substances, especially hydrogen peroxide, which can react with other important molecules in cells to cause damage. They convert these reactive oxygen species into other molecules that are harmless to the cell.
Peroxisomes also perform several specialized functions in plants that they do not perform in animals. Peroxisomes in leaf cells, for example, play a key role in photorespiration. They are also important in seed germination and growth.