Peroxisomes

What are Peroxisomes?

Peroxisome, membrane-bound organelle occurring in the cytoplasm of eukaryotic cells. Peroxisomes play a crucial role in the oxidation of different biomolecules. They also contribute to the biosynthesis of membrane lipids known as plasmalogens. In-plant cells, peroxisomes perform additional functions, including the recycling of phosphoglycolate carbon during photorespiration. Specialized types of peroxisomes have been identified in plants, including glyoxysomes, which function in the conversion of fatty acids to carbohydrates.


Peroxisomes contain enzymes that oxidize certain molecules normally found in the cells, especially fatty acids and amino acids. These oxidation reactions produce hydrogen peroxide, which is the basis of the name peroxisome. However, hydrogen peroxide is potentially harmful to the cell as it is capable of interacting with many other molecules. Peroxisomes therefore also contain enzymes such as catalase, which convert hydrogen peroxide to water and oxygen, thereby neutralizing toxicity. Throughout this way, peroxisomes offer a safe place for the oxidative metabolism of certain molecules.


Creation of Hydrogen Peroxide

Peroxisomes are working in a very specific way. Their enzymes attack and break down complex molecules into smaller molecules. One of the by-products of digestion is hydrogen peroxide (H2O2). Peroxisomes have developed to the point where they can contain the hydrogen peroxide and break it down into water (H2O) and oxygen (O2). Water is harmless to the cell and oxygen can be used for the next digestive reaction.


The cells seem so small and plain when you just look at them, but there's very little that's basic about the cells. Cells carry out different processes internally on a continuous basis. When you start looking deeper inside a cell, you'll find an intricate network of organelles, which are internal cellular structures that perform a cell task.


The organelles in the cell may depend on the type of eukaryotic cell. Some of the organelles you regularly hear about are mitochondria, ribosomes, and a smooth and rough endoplasmic reticulum. I bet I know of an organelle that you know very little about. We 're going to talk about a particular organelle called peroxisomes. Peroxisomes are organelles that produce enzymes to perform their functions. Let's get into the structure of the peroxisomes and their functions.


Peroxisomes Structure
Most organelles are formed by budding off the endomembrane system, but this is not the case with peroxisomes. Peroxisomes are produced by taking proteins and lipids from the cell's cytoplasm. You 're recalling the cytoplasm. It is the gel-like fluid in the cell in which the organelles are suspended.


The influx of proteins and lipids causes the peroxisome to grow in size. Once the peroxisome is large enough, it divides by fission to create two peroxisomes. Peroxisomes are created in this way because they don't have their own DNA to give instructions on how to make the proteins that they need to function. It is therefore essential to build peroxisomes that already contain all the proteins that they need. 


Since peroxisomes are not formed from the endomembrane system, they are bound by a single membrane instead of a double membrane, like most organelles. The end result is a single membrane-bound organelle containing lipids and proteins that act as enzymes.


Peroxisomal Enzymes

Approximately 60 identified enzymes are present in the peroxisome matrix. 

They are responsible for the oxidation reactions leading to the production of hydrogen peroxide. 


The key classes of enzymes are: 

  • Urate oxidase

  • D-amino acid oxidase

  • Catalase


Functions of Peroxisomes

Metabolism of Hydrogen Peroxide: 

Enzymes present in peroxisomes both lead to the production and elimination of H2O2 which is a reactive oxygen species. 


Oxidation of Fatty Acids: 

Oxidation of fatty acids occurs in animal cells, both in peroxisomes and mitochondria, but only limited to peroxisomes in yeasts and plants. 


Oxidation is followed by the development of H2O2 which is decomposed by the enzyme catalase. This is a big source of metabolic energy. 


Biosynthesis of lipids

Cholesterol and dolichol synthesis occurs in both ER and peroxisomes. Bile acid synthesis is produced from cholesterol in the liver.


Peroxisomes comprise plasmalogen synthesizing enzymes, a family of phospholipids that are essential membrane components of the heart and brain tissues. 


Germination of the Seed

Peroxisomes are seeds responsible for converting stored fatty acids into carbohydrates, which are critical to providing energy and raw materials for the growth of germinating plants. 


Suction of Photos

Peroxisomes in leaves, particularly in green ones, carry out a photorespiration process along with chloroplasts.


Degradation of Purines 

Carry out the catabolism of purines, polyamines, and amino acids, particularly uric acid oxidase. 


Bioluminescent

Luciferase enzyme present in fireflies peroxisomes helps in the bioluminescence and thus allows flies to find a companion or a meal.


Key Facts

  • They are membrane-bound spherical bodies of 0.2 to 1.5 μm in diameter found in all eukaryotic organisms, including both plant and animal cells. 

  • They are found to float freely in the cytoplasm in close association of ER, mitochondria or chloroplast within the cell. 

  • They are among the simplest of eukaryotic organelles in the world. 

  • They exist either in the form of a network of interconnected tubules called peroxisome reticulum or as individual micro-peroxisomes.

FAQ (Frequently Asked Questions)

1. Explain Peroxisomes?

Ans - Peroxisomes are small, membrane-enclosed, oxidative-containing cellular organelles involved in a variety of metabolic reactions, including several aspects of energy metabolism.


They are considered to be an important type of microorganism found in both plant and animal cells. 

They have been identified as organelles by the Belgian cytologist Christian de Duve since 1967. 

The first peroxisomes to be discovered were isolated from the leaf homogeneity of spinach. 

They are most commonly found in detoxifying organs, such as the liver and kidney cells. They may, however, be induced to proliferate in response to metabolic needs.

2. What is the Main Function of Peroxisome.

Ans - The key role of peroxisome is the synthesis of lipids and the removal of reactive oxygen species. Other peroxidant functions include: 


Plasmalogen ether glycerolipid synthesis. 

  • Formation of biliary acids, dolichol and cholesterol. 

  • Catabolism of purines, polyamines and amino acids, and detoxification of the species of reactive oxygen 

  • In methylotrophic yeasts, peroxisomes are also involved in the metabolism of methanol and methylamines.