Peroxisomes are membranous sacs that contain some types of digestive enzymes.
Their resemblance to lysosomes caused them to be confused with them until very recently. However, today it is known that peroxisomes differ from lysosomes mainly in the type of enzymes they have.
Peroxisomes, in addition to containing enzymes that break down fats and amino acids, also contain large amounts of the catalase enzyme.
Catalase converts hydrogen peroxide, popularly known as hydrogen peroxide (H2O2), and water and oxygen gas. Hydrogen peroxide normally forms during the breakdown of fats and amino acids, but in large quantities can cause cell damage.
|2 h2O2 + Catalase Enzyme → 2 H2O + O2|
Despite recent findings involving peroxisomes, the function of these organelles in cellular metabolism is still poorly understood. Among other functions, they are believed to participate in cell detoxification processes.
In plants, the germinating leaf and seed cells have special peroxisomes known as glyoxysomes. In leaf cells, these structures act in some reactions of the photosynthesis process, related to the carbon dioxide fixation. In seeds, these organelles are important in transformation of fatty acids into smaller substances, which will eventually be converted into glucose and used by the germinating embryo.