Peroxisome
Overview
A Peroxisome is a type of organelle known as a microbody, which is found in virtually all eukaryotic cells. They are involved in a variety of metabolic processes, including the breakdown of fatty acids through beta-oxidation, the detoxification of harmful substances, and the production and breakdown of hydrogen peroxide. Peroxisomes are bounded by a single membrane and contain a variety of enzymes.
Structure
Peroxisomes are small, spherical organelles that are surrounded by a single lipid bilayer. The interior, or matrix, of peroxisomes is filled with enzymes involved in various metabolic reactions. The size and number of peroxisomes can vary greatly depending on the type of cell and its metabolic activity. For example, cells that are actively involved in lipid metabolism, such as liver and kidney cells, often contain a large number of peroxisomes.
Function
The primary function of peroxisomes is to break down long-chain fatty acids through a process known as beta-oxidation. This process produces acetyl-CoA, which can be used in the Krebs cycle to generate ATP, the primary energy currency of the cell. In addition to fatty acid metabolism, peroxisomes also play a role in the detoxification of harmful substances, including ethanol and other toxic compounds. Peroxisomes also contain enzymes that produce and break down hydrogen peroxide, a reactive oxygen species. This is why peroxisomes were named after the peroxide group (-O-O-).
Biogenesis
Peroxisomes are unique among organelles in that they can replicate themselves. This process, known as peroxisome biogenesis, involves the growth and division of existing peroxisomes. The process begins with the import of proteins from the cytosol, which are then incorporated into the peroxisome membrane. These proteins, known as peroxins, are involved in the growth and division of the peroxisome.
Disorders
Defects in peroxisome function can lead to a number of serious metabolic disorders. These disorders, known collectively as peroxisomal disorders, can result in a variety of symptoms, including developmental delays, liver dysfunction, and neurological problems. Examples of peroxisomal disorders include Zellweger syndrome, adrenoleukodystrophy, and Refsum disease.