peroxisome
/ puh-ROK-sih-some /
Some chemical clean-up jobs are too hazardous to do out in the open, because they create toxic byproducts. The peroxisome is the cell's small, self-contained hazmat unit: a membrane bubble that runs dangerous oxidation reactions safely sealed away from the rest of the cell, then neutralizes the poison it produces.
A peroxisome is a single-membrane organelle filled with enzymes that break down molecules using oxygen. A frequent byproduct of these reactions is hydrogen peroxide, which is toxic — so the peroxisome also carries the enzyme catalase, which immediately converts the hydrogen peroxide into harmless water and oxygen. Among its main duties are breaking down long fatty-acid chains for energy and detoxifying substances; in the liver, peroxisomes help neutralize a meaningful share of the alcohol you drink.
Peroxisomes are easy to confuse with lysosomes because both are small digestive-looking bubbles, but they are different: lysosomes break things down with acid-loving hydrolytic enzymes, whereas peroxisomes use oxygen-based reactions and self-detoxify with catalase. Peroxisomes also do not bud off the Golgi the way lysosomes do; they grow and then split in two to make more of themselves.
If you pour hydrogen peroxide on a cut and it foams, you are watching catalase — the same enzyme peroxisomes use — rapidly turning the peroxide into oxygen bubbles.
The fizz of peroxide on a wound is the same chemistry peroxisomes run internally.
Peroxisomes are not just "small lysosomes" — they run oxygen-based reactions and detoxify with catalase, a chemistry completely distinct from the acid digestion lysosomes perform.