Peroxisome

A peroxisome is a small, single-membrane organelle containing enzymes that catalyze oxidative reactions. Peroxisomes break down fatty acids and amino acids and neutralize toxic compounds (producing hydrogen peroxide, H2O2, as a byproduct, which is then broken down by the enzyme catalase).

• Peroxisomes perform <u>beta-oxidation</u> of long-chain fatty acids, generating acetyl-CoA that can be repurposed by the cell.
• They contain <u>catalase</u>, an enzyme that decomposes hydrogen peroxide into water and oxygen - this protects the cell from oxidative damage due to H2O2 buildup (hence the organelle's name).
• Unlike lysosomes, which are formed in the Golgi apparatus, peroxisomes can self-replicate (bud and divide) and are not part of the endomembrane system.

• If a question mentions breakdown of very-long-chain fatty acids or detoxification of alcohol in cells (especially liver cells) -> think <u>peroxisomes</u> (these organelles oxidize fatty acids and neutralize ethanol).
• Concept trap -> Peroxisomes vs. Lysosomes: peroxisomes carry out oxidation reactions using molecular oxygen (producing H2O2 and then degrading it), whereas lysosomes use acid hydrolases to digest biomaterials. Be sure to distinguish these on exams.
• Genetic tie-in: Disorders like Zellweger syndrome (a peroxisome biogenesis disorder) illustrate peroxisome importance - cells lacking functional peroxisomes accumulate long-chain fatty acids and other toxins, leading to severe developmental issues.