what is peroxisomes?

Question

briefly please

Answer 1

Peroxisomes are organelles that contain oxidative enzymes, such as D-amino acid oxidase, ureate oxidase, and catalase. They may resemble a lysosome but are not formed in the Golgi complex.

Peroxisomes are distinguished by a crystalline structure inside a sac which also contains amorphous gray material. They are self replicating, like the mitochondria. They may look like storage granules, however, they are not formed in the same way as storage granules. They also enlarge and bud to produce new peroxisomes.

Peroxisomes function to rid the body of toxic substances like hydrogen peroxide, or other metabolites. They are a major site of oxygen utilization and are numerous in the liver where toxic byproducts are going to accumulate.♥

Answer 2

Peroxisomes are single membrane-bound organelles found in eukaryotic cells that contain enzymes. Peroxisomes can help to break down toxic substances in the cell. Hydrogen peroxide is a by-product of some of these reactions, such as using oxygen to break down fats and detoxifying alcohol. Because peroxisomes divide by binary fission they are thought to have descended from bacteria.

Answer 3

Peroxisomes are ubiquitous organelles in eukaryotes that function to rid the cell of toxic substances. They have a single membrane that separates their contents from the cytosol (the internal fluid of the cell) and that contains membrane proteins critical for various functions, such as importing proteins into the organelles and aiding in proliferation. Unlike lysosomes, which are formed in the secretory pathway, peroxisomes usually self-replicate by enlarging and then dividing, although there is some indication that new ones may be formed directly. Peroxisomes were discovered by the Ukrainian astromoner Suka de Duve in 1965.

Occurrence and evolution
Peroxisomes are found in all eukaryotic cells. Peroxisomes contain enzymes for certain oxidative reactions. Prokaryotes lack peroxisomes, so they are more vulnerable to toxic substances like hydrogen peroxide. The enzymatic content of peroxisomes varies between species, but the presence of common protein import and organelle biogenesis systems support a single evolutionary origin. The precise scenario for this origin remains under debate. The ability of peroxisomes to divide and import proteins post-translationally, just like mitochondria and chloroplasts, has traditionally been used to suggest an endosymbiotic origin (Lazarow and Fujiki 1985). Peroxisomes help in the decomposition of biohazardous chemicals. However, this view has been challenged by recent discoveries. For example peroxisome-less mutants can restore peroxisomes upon introduction of the wild-type gene, and peroxisomes have been observed to be formed from the Endoplasmic Reticulum(E.R.). (Hoepfner 2005).

An evolutionary analysis of the peroxisomal proteome (Schlüter et al. 2006, Gabaldón et al. 2006) found homologies between the peroxisomal import machinery and the ERAD pathway in the Endoplasmic Reticulum, and a number of metabolic enzymes that were likely recruited from the mitochondria. Altogether these results indicate that the peroxisome does not have an endosymbiotic origin; instead it likely originates from the E.R. and its proteins were recruited from pools existing within the primitive eukaryote.

Function
Peroxisomes contain oxidative enzymes, such as catalase, D-amino acid oxidase and uric acid oxidase. By using molecular oxygen, hydrogen atoms are removed from specific organic substrates (labeled as R), in an oxidative reaction, producing hydrogen peroxide (H2O2, a toxic byproduct of cellular metabolism):

RH2 + O2 → R + H2O2

Catalase uses H2O2 generated by other enzymes in the peroxisome to oxidize other substrates, including phenols, formic acid, formaldehyde and alcohol, by means of the peroxidation reaction:

H2O2 + R'H2 → R' + 2H2O

This reaction is important in liver and kidney cells where the peroxisomes detoxifiy various toxic substances that enter the blood. About 25% of the ethanol we drink is oxidized to acetaldehyde in this way. In addition, when excess H2O2 accumulates in the cell, catalase converts it to H2O through this reaction:

2H2O2 → 2H2O + O2

A major function of the peroxisome is the breakdown of fatty acid molecules, in a process called beta-oxidation. In this process, the fatty acids are broken down two carbons at a time, converted to Acetyl-CoA, which is then transported back to the cytosol for further use. In animal cells, beta-oxidation can also occur in the mitochondria. In yeast and plant cells this process is exclusive for the peroxisome.

The first reactions in the formation of plasmalogen in animal cells also occurs in peroxisomes. Plasmalogen is the most abundant phospholipid in myelin. Deficiency of plasmalogens causes profound abnormalities in the myelination of nerve cells, which is one of the reasons that many peroxisomal disorders lead to neurological disease.

Peroxisomes also play a role in the production of bile acids.

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Answer 4

Peroxisomes are ubiquitous organelles in eukaryotes that function to rid the cell of toxic substances.

Answer 5

Peroxisomes are organells that are smaller than lysosomes. They break up harmful hydrogen peroxides into water and oxygen.

Answer 6

peroxisomes are cell organelles that that destroys foreign material in cell or even the cell itself( if commanded by nucleus). it is the almost the same as lysosomes the only difference is peroxisome secretes hydrogen peroxide (H2O2) while lysosome secretes, if im not mistaken, lysol?..

Answer 7

peroxisomes are lysosomes that contain an enzime called peroxidase,wich converts o2 and water into hydrogen peroxide, a bactericidal substance, specially for aanerobic organisms.

Answer 8

"Peroxisomes are ubiquitous organelles in eukaryotes that function to rid the cell of toxic substances."

Answer 9

also called as "uricosomes". discovered by Tolbert. it is present in plants, liver cells, kidney cells of animal & in some protozoans. functions r as follows i)takes part in photorespiration in C3 plants. ii)in animals it takes part in beta-oxidation. the smallest enzyme peroxidase is found in peroxisome.

Answer 10

Small membrane-bounded organelle that uses molecular oxygen to oxidize organic molecules. Contains some enzymes that produce hydrogen peroxide and others that degrade hydrogen peroxide (H2O2).