MICROBODIES: Definition, Types, Examples, Diagram, Functions

Microbodies are defined as small single-membrane-bound organelles that are present in eukaryotic cells and play a vital role in a great variety of metabolic pathways, such as detoxification and lipid metabolism. They are meaningful in maintaining cellular homeostasis and protecting cells against damage from reactive oxygen species. Microbodies is a topic of the chapter Cell: The Unit of Life in Biology.

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This Story also Contains

1. What are Microbodies?
2. Structure of Microbodies
3. Types of Microbodies
4. Biogenesis of Microbodies
5. Microbodies in different Organisms
6. Clinical and Biotechnological Significance
7. Recommended video on Microbodies

What are Microbodies?

Microbodies are small membrane-bounded organelles in eukaryotic cells, mainly associated with metabolic processes, including detoxification, fatty acid oxidation, and hydrogen peroxide breakdown. They were first identified by Christian de Duve in the 1950s when he defined peroxisomes and later glyoxysomes, further elaborating on the huge importance these organelles have in cellular metabolism and defence.

Structure of Microbodies

They are small, spherical organelles that are bounded by a single membrane of a lipid bilayer, which maintains the special environment within the microbodies. The membrane consists of phospholipids plus proteins that enable the free transfer of both metabolites and enzymes into and out of the microbody. The microbody contains various enzymes, among them are catalase and oxidases that are contained in the peroxisomes. As such, these enzymes are thus equipped to carry out important metabolic functions, which encompass the oxidation of fatty acids, detoxification, and conversion of carbohydrates.

Also Read-

• MCQ Practice on Microbodies
• Cell: The Unit Of Life
• Cytoplasm
• Cell wall

Types of Microbodies

Microbodies are mainly divided into two types:

Peroxisomes

• These microbodies contain enzymes for peroxide biosynthesis.

• These are present in both the plant cells and animal cells in close proximity to ER, mitochondria and chloroplasts.

The following enzymes are present in the peroxisomes:

1. Urate oxidase

2. D-amino acid oxidase

3. Α-hydroxy acid oxidase

4. Β- hydroxy acid oxidase

In the presence of molecular oxygen, hydrogen peroxide is formed, which is metabolised by the catalase enzyme.

Functions of Peroxisomes

• Peroxisomes are mainly concerned with fatty acid metabolism.

• They carry out oxidation reactions that result in the formation of hydrogen peroxide.

• This hydrogen peroxide is used to detoxify the toxic compounds. Peroxisomes in the liver help in the detoxification of alcohol.

• In plants, the peroxisomes play an important role in the mobilization of fatty acids during seed germination. The fatty acids are converted to sugars which provide energy.

• Peroxisomes also help to recycle phosphoglycolate - a by-product of the Calvin cycle. This is a very important function as if the recycling didn't happen a lot of the cell's energy and carbon would be lost.

Glyoxysomes

• These are specialised single membrane-bound microbodies found in plants (Particularly in fat-storing tissues) and filamentous fungi.

• The key enzymes of the glyoxylate cycle - isocitrate lyase and malate synthase are present in the glyoxysomes.

• They are responsible for the breakdown of fatty acids and their conversion into sugars through gluconeogenesis.

• They are believed to be special types of peroxisomes.

Functions of Glyoxysomes

• The glyoxylate cycle results in a conversion of stored lipids into carbohydrates during seed germination; among other places, this process occurs in glyoxysomes.

• They do so by facilitating the conversion of fatty acids to succinate, which is a precursor for entry into the Krebs cycle and full oxidation to produce energy.

Biogenesis of Microbodies

Microbodies are known to originate in and develop within the cell through vesicles budding off from the endoplasmic reticulum (ER). The ER is the membrane source as well as the initial source for the enzymes. Further maturation, with the help of the Golgi apparatus, and sorting of the enzymes is also done with the assistance provided in this process. Genetic factors have been elucidated as a factor for microbody participation. Certain genes encode the proteins and enzymes essential for carrying out the functions of microbodies. These properly functioning genes should then be responsible for the correct assembly, targeting enzymes, and proper regulation of microbodies within the cell.

Microbodies in different Organisms

Read about the microbodies in different organisms

Microbodies in Plants

• Peroxisomes take part in photorespiration and aid in the removal of hydrogen peroxide.

• Glyoxysomes are primary in the conversion of the lipid bodies stored by the plants. This is a further conversion of the lipid bodies into carbohydrate form.

Microbodies in Animals

• Peroxisomes are the major types of microbodies in animal cells.

• They are therefore crucial for lipid breakdown and detoxification of the body from toxic hydrogen peroxide.

Microbodies in Fungi

• Peroxisomes make up most of the microbodies in the fungi.

• These are involved in a variety of metabolic functions similar to beta-oxidation of fatty acids to detoxification of reactive oxygen species.

Clinical and Biotechnological Significance

Microbodies are kept at the core of human health. Some of the fatal metabolic complications are linked with peroxisomal disorders due to the non-functionality of microbodies. Microbodies are exploited for their enzymatic activities such as biofuels and bioplastics production. Recent research related to the action of gene therapy and the induced engineering of microbodies to enhance their metabolic capabilities for their applications in therapeutics and industry is ongoing.

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Recommended video on Microbodies