Peroxisomes

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Chemicals converted to Hydrogen Peroxide

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Catalase

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Peroxisomes

Like lysosomes, peroxisomes are special spherical vesicles made of fatty bilayer membranes and are present in most eukaryotic cells. They serve much the same function, but do so and are formed in different ways. Peroxisomes bud off from the endoplasmic reticulum and replicate daughter peroxisomes from fission. ER has a role in the ongoing maintenance of peroxisomes as well, in the form of consistent protein transport.  Their origin being linked to free ribosomes and the fact that they make copies of themselves by fission indicate that they resemble organelles like mitochondria just as much as they do lysosomes. 

peroxixomeStill, much like lysosomes, they derive over 50 various enzymes from the ER. As such, their primary role in metabolism is the catabolism part – the breaking down of foods – and the reduction of oxidative stress – a byproduct of cell metabolism and growth that causes the gradual deterioration of cell structure (or aging). Oxidative stress also results in more oxidative stress, so it is like a snowball rolling downhill and collecting increasingly more snow as it rolls.  As is the case with lysosomes, the two-layer membrane offers the cell protection from the dangerous chemicals contained in the peroxisome vesicles.

While lysosomes and peroxisomes both play key roles in the cell’s metabolism, they work on different types of foods.  Peroxisomes break down fatty acid chains, uric acids, bile acids, amino acids, certain types of sugars, a special type of lipid called cholesterol, and some other nutrients.  In certain types of cells, peroxisomes only break these molecules down partly, after which they are transported to the mitochondria for further processing. 

In plant and yeast cells, peroxisomes don’t rely on the aid of mitochondria. In cells that undergo photosynthesis and photorespiration, peroxisomes play a part in their version of cellular metabolism.  As a byproduct of metabolism, peroxisomes release hydrogen peroxide, which a reactive oxygen species. However, they are also equipped with an antioxidant – a chemical that prevents oxidative stress – the enzyme catalase. 

Hydrogen peroxide poses a threat to the cell because it is highly reactive with its components, and upon chemical bonding, it essentially snatches those components from the cell, causing damage to the cell.  Antioxidants prevent oxidative stress by bonding or otherwise reacting with the reactive oxygen species so that they can’t harm the cell.

Summary

Peroxisomes are special vesicles that formed from the endoplasmic reticulum. Peroxisomes can replicate like mitochondria. Their most important function is metabolism, which is very similar to lysosomes, except that peroxisomes break down different substances. However, in the breaking down of certain substances / proteins, reactive oxygen species like hydrogen peroxide may result but unlike many other organelles, peroxisomes clean up their own mess – i.e., they use their own enzyme catalase to neutralize hydrogen peroxide. This gives peroxisomes a place as an important component for the metabolism of the cell.

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