Question

What is pereoxisome and its function??

And what is function of nucleolus?

Answer 1

Functions of Peroxiomes

• 
  Peroxisomes are involved in the formation and decomposition of hydrogen peroxide and the word peroxisome is actually derived from hydrogen peroxide. Peroxisome contains oxidative enzymes, such as catalase, D-amino acid oxidase and uric acid oxidase. They use molecular oxygen to remove hydrogen atoms from a specific organic substrate (R) in an oxidative reaction. It produces hydrogen peroxide (H₂O₂ is a toxic byproduct of cellular metabolism).

RH₂ + O₂ ==>> R + H₂O₂

• Catalases uses this H₂O₂ in the peroxisome to oxidize other substrates like phenols, formic acid, formaldehyde, and alcohol:
  H₂O₂ + R'H₂ ==>> R' + 2H₂O
  This reaction is important in liver and kidney cells where the peroxisomes detoxify various toxic substances that enter the blood. In addition, when excess H₂O₂ accumulates in the cell, catalase converts it to H₂O through this reaction:
  2H₂O₂ ==>> 2H₂O + O₂
• Peroxisomes are important for lipids metabolism. In humans, oxidation of fatty acids greater than 18 carbons in length occurs in peroxisomes. In yeast, all fatty acid oxidation occurs in peroxisomes. A major function of peroxisomes is the breakdown of fatty acid molecules in a process called beta-oxidation. In this process, the fatty acids are broken down into Acetyl-CoA. It is then transported to back to the cytosol for further use.
• Peroxisomes contain the first two enzymes required for the synthesis of plasmalogens (myelin sheath).
• Peroxisomes also play important roles in cholesterol and bile acid synthesis, purine and polyamine catabolism, and prostaglandin metabolism.
• In plants, peroxisomes are required for photorespiration.

Function of Nucleolus

The nucleus of many eukaryotic cells contains a structure called a nucleolus. As the nucleus is the "brain" of the cell, the nucleolus could loosely be thought of as the brain of the nucleus. The nucleolus takes up around 25% of the volume of the nucleus. This structure is made up of proteins and ribonucleic acids (RNA). Its main function is to rewrite ribosomal RNA (rRNA) and combine it with proteins. This results in the formation of incomplete ribosomes. There is an uninterrupted chain between the nucleoplasm and the interior parts of the nucleolus, whichoccurs through a system of nucleolarpassages. These passages allow macromolecules with a molecular weight up to 2,000 kDato be easily circulated throughout the nucleolus. Because of its close relationship to the chromosomal matter of the cell and its important role in producing ribosomes, the nucleolus is thought to be the cause of a variety of different human diseases.