Microbodies

Introduction

All living organisms possess cells. It is most important structurally, biologically, and functionally. By division of cells, they increase the numbers and form all the structures in the body. There are three essential parts present in a cell, namely the plasma membrane, cytoplasm, and nucleus. Cell organelles are present in the cytoplasm. Different cell organelles that are present in the cytoplasm have different functions. Microbodies are cell organelles that are present both in plant and animal cells. In this tutorial, we will learn about microbodies in depth.

What are Microbodies?

The term microbody was introduced and discovered by scientists Johannes Rhodin in 1954. Microbodies are cell organelles that are present both in plant and animal cells. They are small, spherical, or ellipsoidal in shape, and present in the cytoplasm of eukaryotic cells. Microbodies are membrane-bound organelles that accommodate various types of enzymes. They have specific functions like lipid metabolism, protein degradation, and synthesis of vitamins. Glyoxysomes and peroxisomes are the two main types of micro bodies.

Structure

The structure of microbodies is described below

• Microbodies are small, spherical, or ellipsoidal structures that are present in the cytoplasm of all eukaryotic cells.

• They have a single membrane and are sometimes called cytosomes.

• The diameter of these cell organelles is 0.2-1.5 $\mathrm{\mu}$m.

• A microbody is usually a vesicle with a spherical shape that can only be seen with the help of an electron microscope.

• The single membrane is made up of a phospholipid bilayer and its matrix contains intracellular material including many proteins and enzymes which help in many cell processes but they don't self-replicate.

• They do not contain genetic material.

• Sometimes a crystalloid core is also present.

Classification

Microbodies are small organelles and are bound by a single membrane. They are formed by the endoplasmic reticulum. Microbodies are found in plants, protozoa, fungi, liver, and kidney cells of humans.

Peroxisomes

• Peroxisomes are small membrane-bound cell organelles.

• It contains enzymes that help in a variety of metabolic reactions.

• It helps in energy metabolism.

• Peroxisomes in animal cells are involved in fat metabolism and peroxide metabolism.

• They are involved in many biochemical pathways essential for cells.

Glyoxysomes

• Glyoxysomes, the term was originally named by Harry Beevers and colleagues.

• They are specialized types of plant peroxisomes.

• Glyoxysomes are available in fungi as well as germinating oil seeds like castor seed, ground seed, etc.

• They are not found in animal cells.

• They contain glyoxylate cycle enzymes.

• Glyoxysomes are typically present in the cotyledons or endosperms of germinating fatty seeds.

• Other enzymes such as glycolate oxidase and several aminotransferases exist in glyoxysomes.

Spherosome

• Spherosomes are single membranes.

• They are small and spherical cell organelles, with a diameter of about 0.5-1.0 $\mathrm{\mu}$m.

• They are specialized to synthesize and store lipids. For example, the cells of cotyledons of mustard and groundnut.

• They are often present in fat-storing plant cells but are also abundant in oilseeds, for example, maize root tip, tobacco endosperm, etc.

• They are also known as plant lysosomes and oleosome. Lysosomes help in the disintegration and degradation of proteins, lipids, and carbohydrates.

Lomesome

• They are discovered by Moor and McAlear.

• They are found between the cell wall and plasma membrane of fungal and plant cells.

• These organelles are also known as the Paramural bodies.

Visibility and Distinguishing Factor

The visibility and distinguishing factor of microbodies are listed below −

• All the microbodies have the same characteristics but their metabolic rates vary.

• Metabolic roles are a type of cell and development stage.

• Catalase that is found in cell organelles is visible in the electron microscope.

• Protein is present in microbodies in a dense granular matrix.

• In this type of organelle, internal membranous structures are absent but some of them contain striking proteinaceous crystals.

• With the help of an electron microscope, protein structure can be observed.

• Peroxisomes or glyoxysomes are visible under a fluorescence microscope.

• Microbodies’ internal matrix structure is very simple; for this reason, they can easily differentiate from chloroplast and mitochondria.

Function of Microbodies

The function of microbodies are listed below

• Detoxifying the alcohol in liver cells is carried out by peroxisomes.

• In animal cells peroxisomes perform functions of fat metabolism and peroxide metabolism.

• The oxidation of fatty acids provides a major source of metabolic energy.

• In animal cells, peroxisomes perform photorespiration along with mitochondria and chloroplast.

• They are involved in lipid catabolism and metabolism of D-amino acids, polyamines and bile acids.

• Glyoxisomes determine the production of succinate by means of glyoxylate cycle enzymes.

• Glyoxysomes also facilitate the conversion of fats into carbohydrates while avoiding the decarboxylative steps of the Krebs cycle.

• $\mathrm{\beta}$ - oxidation of fatty acids is done in glyoxysomes.

Peroxisome Biogenesis Disorder in Human

The peroxisome function is affected due to the inborn error of peroxisomes. It is a rare genetic disorder. Peroxisome function helps in the normal metabolism of fats and certain amino acids. Inborn errors of peroxisome are mainly due to defective genes that encode the enzyme for fatty acid metabolism. As a result, harmful products like hydrogen peroxide are produced as a by-product. It causes liver disease, delay in development , loss of hearing and vision problems.

Conclusion

All living organisms possess cells. It is most important structurally, biologically, and functionally. Different cell organelles that are present in the cytoplasm have different functions. Microbodies are cell organelles that are present both in plant and animal cells. They have specific functions like lipid metabolism, protein degradation, and synthesis of vitamins. Glyoxysomes and peroxisomes are the two main types of microbodies.

FAQs

Q1. What do you understand about mitochondria?

Ans. Mitochondria is a membrane-bound cell organelle. It is known as the powerhouse of the cell. It generates energy for the cells.

Q2. What is an endoplasmic reticulum?

Ans. The endoplasmic reticulum is a network of membranous tubules filled up with fluids. It can be smooth or rough. It takes part in transportation and protein synthesis.

Q3. What do you mean by cell organelles?

Ans. Organelles are present inside the cells and they perform various specific functions. The term organelles are obtained from the organs and refer to different chambers that are present within the cells that perform specific functions. Organelles perform one or more functions in the cell. Organelles are both non membrane-bound and membranebound and are found in both eukaryotes and prokaryotes.

Q4. What do you understand by lipid?

Ans. Lipids are hydrocarbon molecules. Lipids form the building framework of the structure and function of cells of living organisms. Due to its nonpolar nature, it is insoluble in water. Food rich in lipids includes oil, butter, cheese, fried food, etc. Lipids are synthesized in the liver.

Q5. Name some common liver diseases.

Ans. The most common causes of liver diseases are infection, heredity, lifestyle, and too much consumption of alcohol. The most common liver diseases are hepatitis A, hepatitis B, hepatitis C, liver cirrhosis, Wilson diseases, hemochromatosis, etc.