Peroxisomes (microbodies) are membrane bounded organelles that contain enzymes involved in the degredation of fatty acids and amino acids. They also contain the enzyme catalase. The enzymes in the peroxisomes are synthesized on the RER and are sorted into the peroxisomes in the golgi apparatus
Peroxisomes are membrane bounded vesicles of the cytoplasm of animal cells. Plant cells have similar vesicels called gyloxisomes. Peroxisomes are about the same size, or slightly larger than lysosomes. However, peroxisomes do not have proton pumps in their membranes nor do they have the variety of hydrolytic enzymes found in lysosomes.
Peroxisomes contain enzymes that degrade fatty acids and amino acids. In doing so they produce hydrogen peroxide.
Hydrogen peroxide is very toxic because it is unstable and spontanously degrades to produce compounds called free radicals. Free radicals are very reactive because they have unpaired electrons and will react with a variety of cellular macromolecles and alter their structure.
Fortunately peroxisomes contain the enzyme called catalase that degrades hydrogen peroxide to the less dangerous oxygen and water.