A microbody (or cytosome) is a type of

organelle In cell biology, an organelle is a specialized subunit, usually within a cell (biology), cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as Organ (anatomy), organs are to th ...

that is found in the cells of plants, protozoa, and animals. Organelles in the microbody family include peroxisomes, glyoxysomes, glycosomes and hydrogenosomes. In vertebrates, microbodies are especially prevalent in the

liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

and

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

. Many membrane bound vesicles called microbodies that contain various enzymes, are present in both plant and animal cells.

Structure

Microbodies are different type of bodies present in the cytosol, also known as cytosomes. A microbody is usually a vesicle with a spherical shape, ranging from 0.2-1.5 micrometers in diameter."Microbodies." Molecular Biology of Plant Cells. Ed. H. Smith. N.p.: University of California, 1978. 136-54. Print. Microbodies are found in the

cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...

of a cell, but they are only visible with the use of an

electron microscope An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing it ...

. They are surrounded by a single phospholipid bilayer membrane and they contain a matrix of intracellular material including

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

s and other proteins, but they do not seem to contain any genetic material to allow them to self-replicate.

Function

Microbodies contain enzymes that participate in the preparatory or intermediate stages of biochemical reactions within the cell. This facilitates the breakdown of fats, alcohols and amino acids. Generally microbodies are involved in detoxification of peroxides and in photo respiration in plants. Different types of microbodies have different functions:

Peroxisomes

A peroxisome is a type of microbody that functions to help the body break down large molecules and detoxify hazardous substances. It contains enzymes like oxidase, react hydrogen peroxide as a byproduct of its enzymatic reactions. Within the peroxisome, hydrogen peroxide can then be converted to water by enzymes like

catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting ...

and peroxidase. Discovered and named by Christian de Duve.

Glyoxysomes

Glyoxysomes are specialized peroxisomes found in plants and

mold A mold () or mould () is one of the structures that certain fungus, fungi can form. The dust-like, colored appearance of molds is due to the formation of Spore#Fungi, spores containing Secondary metabolite#Fungal secondary metabolites, fungal ...

, which help to convert stored lipids into carbohydrates so they can be used for plant growth. In glyoxysomes the fatty acids are hydrolyzed to acetyl-CoA by peroxisomal β-oxidation enzymes. Besides peroxisomal functions, glyoxysomes also possess the key enzymes of the glyoxylate cycle.

History

Microbodies were first discovered and named in 1954 by Rhodin. Two years later in 1956, Rouiller and Bernhard presented the first worldwide accepted images of microbodies in liver cells. Then in 1965, Christian de Duve and coworkers isolated microbodies from the liver of a rat. De Duve also believed that the name microbody was too general and chose the name of peroxisome because of its relationship with hydrogen peroxide. In 1967, Breidenbach and Beevers were the first to isolate microbodies from plants, which they named glyoxysomes because they were found to contain enzymes of the glyoxylate cycle.

References

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