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Microbodies

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  • Last Updated : 04 Sep, 2022
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The cell is the primary structural and functional unit of all living organisms. Biomolecules such as proteins and nucleic acids are found in the cytoplasm of each cell, which is encircled by a membrane.

Protein synthesis, DNA repair, replication, and motility are just a few of the tasks that cells can carry out within the cell and for which they can evolve specialised functionalities. Cells can specialise and migrate around within the cell. The bulk of cells is measured in micrometres due to their modest size.

Microbodies

Consequently, a microbody is a cytoplasmic organelle with an approximately spherical form. They are compounds-degrading enzymes that are contained in a single membrane. They are believed to function as momentary centres of metabolic activity. Microbodies can take many different shapes. Among these are Woronin bodies, peroxisomes, glycosomes, and glyoxysomes.

Structure of Microbodies

These “microbodies” are the bodily components found in a cell’s cytoplasm. They are also referred to as cytosomes. A microbody is typically a spherical vesicle with a diameter of between 0.2 and 1.5 micrometres. Microbodies can be seen in a cell’s cytoplasm, however, they can only be viewed under an electron microscope. They are surrounded by a single phospholipid bilayer membrane and have an intracellular protein and enzyme matrix, but it doesn’t appear that they have any genetic material that would allow them to self-replicate.

Lysosome

 

Classification of Microbodies

The enzymes found in microbodies participate in the preliminary or intermediate stages of a variety of biochemical processes taking place inside the cell. These enzymes promote the oxidation of fatty acids, alcohols, and amino acids. Microbodies often play a big role in plants’ photorespiration and peroxide detoxification. Microbodies are divided into categories based on their functions. Important microbodies include the following: Woronin bodies, Glyoxysomes, Peroxisomes, and Glycosomes.

Peroxisomes

  • The organelle identified by Christian de Duve in 1965 is the peroxisome.
  • It was found with the use of the fractionation method.
  • Cells from plants and animals both contain these microbodies.
  • Organelles such as the endoplasmic reticulum, mitochondria, and chloroplasts are situated in close proximity to it.
  • It is found in all eukaryotic cells and is particularly prevalent in the liver and kidney cells.
  • The endoplasmic reticulum gave rise to the 70–100 peroxisomes that make up the photosynthetic cell.
  • The peroxisomes can vary in size, shape, and diameter.
  • The interior matrix of these structures, which might be granular or contain uniformly spaced fibrils, is covered by the outer membrane.
  • Oxidative enzymes such as urate oxidase, hydroxy acid oxidase, and hydroxy acid oxidase are present in these microbodies.
  • The process results in hydrogen peroxide, which another enzyme known as catalase instantly metabolises.

Structure

  1. Using a catalase cytochemical reaction, peroxisomes—membrane-bound, spherical or ovoid organelles—can be identified in cells. Larger peroxisomes can be seen in the laboratory in the hepatocytes.
  2. The endoplasmic reticulum is frequently in its immediate vicinity.
  3. In stain preparations, they showed minute organelles with a diameter of 0.1 to m.
  4. Urate oxidase is found in the nucleoid and crystal structure of the core. On the other hand, human cell peroxisomes are nucleoid-free.

Function

  1. The long-chain fatty acids are oxidised by enzymes found in peroxisomes.
  2. They take part in the manufacture of cholesterol by using their enzyme.
  3. They are engaged in the detoxification of chemicals that injure the cells in the body, like ethanol and hydrogen peroxide.
  4. The synthesis of plasmalogen is started by certain of its peroxisomal enzymes. The majority of myelin’s phospholipids are made up of this material.
  5. Additionally, photorespiration uses in plant cells.

Glyoxysomes

  • These are the microbodies that contain the fatty acid oxidation and glyoxylate pathway enzymes.
  • Breidenbach made this discovery in 1967.
  • These organelles are regarded as a distinct variety of peroxisomes.
  • These are the biggest microbodies and are only present in plants.
  • Glyoxysomes are the structures that are present in the cells of some fungi and the fatty seeds that are germination (such as castor, groundnut, etc.) up until and unless the stored fat is eaten.
  • Enzymes are found inside glyoxysomes, which have a single outer membrane.
  • Acetyl CoA is created when fatty acids are -oxidized.
  • The glyoxylate cycle breaks down the latter to create carbs.
  • After serving their purpose, the glyoxysomes are changed into peroxisomes.
  • For the purpose of lipid mobilisation and breakdown, these structures emerge in senescent plant tissues.

Glycosome

The glycosome is a membrane-enclosed organelle that houses the glycolytic enzymes and a substantial proteinaceous matrix. A few protozoan species that cause Leishmania, Chagas’s disease, sleeping sickness, and other human pathogenic trypanosome diseases have glycosomes. According to theory, it descended from the peroxisome. Peroxisomal and glycolysis enzymes are found in glycosomes.

Woronin Body

The woronin body is a dense core microbody produced from peroxisomes that are shielded by a double-layered membrane. It bears the name Mikhail Stepanovich Woronin, a Russian botanist. In filamentous Ascomycota, it is found close to the septae that divide the hyphal compartments. These entities’ primary purpose is to close off the septal pores after hyphal injury. It prevents cytoplasm from being lost in the areas of damage. The woronin bodies can range in size from 100 nm to more than 1 μm. In certain species, they are visible under a light microscope.

Peroxisome Biogenesis

The Zellweger syndrome spectrum (ZSS) disorders and rhizomelic chondrodysplasia punctata (RCDP) type 1 are two clinically distinct subtypes of the diverse set of autosomal recessive human illnesses known as peroxisome biogenesis disorders (PBDs). At least 14 different PEX genes, which encode proteins involved in peroxisome assembly and proliferation, can develop abnormalities, which lead to PBDs. These ZSS diseases are linked to thirteen of these genes. Different approaches to finding the causal gene abnormalities have been developed as a result of the genetic variety across PBDs and the impossibility to determine which of the 13 known PEX genes is deficient from the biochemical and clinical characteristics of a patient with ZSS. The most frequently mutant exons of the various PEX genes are examined in a PEX gene screen, which also includes PEX cDNA transfection complementation experiments and sequencing of the PEX genes thus discovered. The advantages of DNA testing for PBDs include carrier screening for close family members, early prenatal testing or preimplantation genetic diagnosis in families at risk for ZSS illnesses, and insight into genotype-phenotype correlations, which may eventually help to enhance patient care. 

Function of  Microbodies

  1. Microbodies participate in numerous cell biochemical processes.
  2. The breakdown of lipids, amino acids, alcohol, etc. is made possible by the enzymes found in microbodies.
  3. They participate in plants’ photorespiration.
  4. In microbodies, peroxides are detoxified.

FAQs on Microbodies

Question 1: Which tasks does the peroxisome do primarily?

Answer:

  • Peroxisomes metabolise a number of hazardous chemicals found in animal cells, including nitrite, phenols, formaldehyde, formic acid, methanol, and ethanol. Inside liver cells, 25% of alcohol eaten is detoxified.
  • Xenobiotics are uncommon compounds that are digested by peroxisomes rather than by regular enzymes.
    Peroxisomes degrade long and branched-chain fatty acids like prostaglandins.
  • For transit in the root nodules, this organelle transforms fixed nitrogen into ureids.
  • Photorespiration is a process carried out by plant peroxisomes, which are present in the chloroplast and mitochondria of photosynthetic cells.
  • Chloroplasts release glycolate, which is then taken up by peroxisomes and converted into glyoxylate by oxygen. As a byproduct of the procedure, hydrogen peroxide is created.

Question 2: What are microbodies? 

Answer:

Some eukaryotic creatures have a specific form of organelle-like body called a microbody (plants and animals). These entities, which have a vesicle-like spherical form and contain enzymes for unusual biological processes, are found in the cell cytoplasm (such as alpha oxidation of fatty acids). Peroxisomes (found in human and other animal cells), glycosomes (found in protozoan cells), glyoxysomes (found in plant cells), woronin bodies, etc. are a few examples of the recognised microbodies found in eukaryotes.

Question 3: What function do microbodies play in eukaryotic cells?

Answer:

Throughout the animal and plant kingdoms, microbodies have a variety of functions. Here are a few of them:

  • Peroxisomes are a type of microbody found in animal cells. They act as the location of fatty acid alpha oxidation. Additionally, they contain the enzymes catalase, oxidase, and peroxidase, which convert damaging hydrogen peroxide byproducts from other chemical reactions into water molecules.
  • Glyoxysomes, which are microbodies found in plants, hydrolyze fatty acids to produce acetyl-CoA. Additionally, they have vital enzymes for the Glyoxylate cycle.

Question 4: Explain the distinction between peroxisomes and glyoxysomes.

Answer:

Peroxisomes and glyoxysomes are examples of microbody structures. However, peroxisomes are exclusive to animal cell types, whereas glyoxysomes are primarily found in plant and filamentous fungi (mould) cells. As glyoxysomes include the enzymes required for the glyoxylate cycle, whereas peroxisomes might not, they also differ in their enzymatic content. The enzymes needed to break down hydrogen peroxide, which are not present in plant cells, are found in peroxisomes.

Question 5: What are inborn errors? What inborn errors are found in the case of microbodies?

Answer:

The term “inborn mistakes” refers to the inheritance of defective genes that might result in rare genetic illnesses in the offspring and disrupt or only partially normalise the metabolic processes of the cell. Galactosemia is a common example of an inborn error; other inborn mistakes are more uncommon. Microbody-related inborn mistakes are rather few. However, in humans, the peroxisome can acquire biogenesis problems that can result in a wide range of secondary illnesses, such as hepatomegaly, aberrant bone calcification, etc.

Question 6: Which function do peroxisomes serve in plants?

Answer:

  1. Photorespiration is a process carried out by plant peroxisomes, which are present in the chloroplast and mitochondria of photosynthetic cells.
  2. Chloroplasts release glycolate, which is then taken up by peroxisomes and converted into glyoxylate by oxygen. As a byproduct of the procedure, hydrogen peroxide is created.
  3. It transforms glyoxylate into the amino acid glycine. The amino acid serine and carbon dioxide are then produced as the glycine condenses.

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