A peroxisome is a specialized structure inside a cell which helps to rid the body of the host organism of toxins. In animals, peroxisomes are often especially concentrated in the neighborhood of the liver and kidneys, the filtration centers for toxins. In plants, peroxisomes assist with photosynthesis. In either instance, a peroxisome disorder can be a serious problem, as these structures are crucial to the wellbeing of much of life on Earth.
Like other specialized structures inside a cell, a peroxisome is considered to be an example of an organelle. Essentially, organelles are like miniature organs inside the cell, just as their name suggests, and they perform many of the same functions that major organs do, only on a much smaller scale. When viewed under a microscope, it is possible to see that peroxisomes are roughly spherical in shape, and they are surrounded by an envelope of lipids and proteins which protects the rest of the cell from the activity inside the peroxisome.
These structures were first firmly identified in 1967, a decade after they had been described by a Swedish doctoral student. The peroxisome is rather a unique organelle, because it is capable of replicating itself, much like DNA. When more peroxisomes are needed in a cell, the existing peroxisomes can grow and then split themselves to meet the need.
When a peroxisome absorbs a toxin, it oxidizes it, converting it to hydrogen peroxide. However, hydrogen peroxide isn't a very healthy thing to have floating around in the body in large amounts, so peroxisomes are also capable of breaking down hydrogen peroxide, turning it into useful water and oxygen which can be utilized by the cell for a variety of tasks or expressed, if the body has an excess.
Peroxisomes are part of the process of cell metabolism, which keeps cells running smoothly to ensure that they have enough energy to perform their functions. With peroxisomes on the fritz, people can develop disorders related to a buildup of lipids and other toxins in their bodies. This can manifest in the form of a variety of conditions, including the neurological disorder known as Zellweger Syndrome.