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Nucleus Function Structire and Definiton

The human body is full of cells. There are cells found on every inch of a human's body, everywhere from hair to toenails. However, a cell contains various parts in itself, each one of them has different structures and functions. Among many components found in a cell, one of the most important is the nucleolus. One can find them inside the nucleus of cells, especially eukaryotic cells.

A nucleolus is defined as the distinct structure present in the nucleus of a eukaryotic cell. It helps in assembling ribosomes, senses cellular stress, and one of its notable functions is it takes part in the modification and transfer of RNA.

The nucleolus majorly consists of proteins and RNA. We can find them formed around some specific chromosomes and regions.

Structure of the Nucleolus

The nucleolus structure is not a diverse one. It has different components that contribute to its function. Apart from DNA and RNA, the nucleolus is also a vital part of the nucleus. Some main parts found in every nucleolus include proteins, deoxyribonucleic acid, and ribonucleic acid.

In every eukaryotic cell, the nucleolus has a very organized structure, with its main ultrastructural parts.

These four parts are Fibrillar centres, Granular components, Dense fibrillar components, and finally, nucleolar vacuoles.

  • Fibrillar centres create ribosomal proteins.
  • The granular components provide rRNA that binds to the ribosomal protein. After the various processes, the formation of ribosomes occurs.
  • The dense fibrillar parts have RNA, and they connect to the proteins. Scientists have found the above-mentioned components in animals, and plants alike, but the nucleolar vacuoles are found only in vegetation and plants.

Functions of Nucleolus

1. Ribosome Production and Protein Synthesis

  • The nucleolus found inside a nucleus contributes to about 25% of the volume of a nucleus, and it takes part in the production of ribosomal subunits.
  • After that, they assemble the subunits and form ribosomes. So, nucleolus plays a major part in producing ribosomes for eukaryotic cells and in synthesizing proteins.
  • The process of Ribosome Production: The ribosomal RNA, rRNA, is obtained and transcribed from DNA, then it is processed and separated into three more mature RNAs. They are packaged into proteins, which are small and large subunits of ribosomal. After that, they are organized well. They go into the cytoplasm and are used in protein synthesis.

2. Nucleolus are not static structures, but they get disassembled during mitosis. The nucleus formation is the direct result of rRNA transcription and processing, but they do not cause the expression of rRNA genes. But according to new research, it has been found that nucleolus can also be involved in other cellular processes. It helps the human body in modifying and assembling the RNPs (ribonucleoproteins).

3. It helps in regulating protein synthesis and controlling the process of ageing.

4. It also assists in exporting no ribosomal RNAs.

Hence, the nucleolus can be considered as the place where ribosomes are made, and protein is synthesized along with its various other purposes.

Differences between Nucleus and Nucleolus

People often get confused between nucleus and nucleolus. The nucleolus is present inside the nucleus, and apart from that, there are many differences.

The nucleus is larger than a nucleolus and is bound by a nuclear envelope. The nucleus has chromosomes and is rich in DNA. A nucleolus does not have any limiting membrane and doesn’t contain chromosomes. And a nucleolus is rich in RNA.

Did you know?

Scientists and microbiologists use techniques like photobleaching and fluorescent recovery or fluorescent protein tagging to study the location and structure of nucleolus. Many use these techniques since it provides a clear image of the nucleolus for anyone to observe and understand.

The nucleolus found in many plants has a considerably high amount of iron concentration in them. It is unlike the nucleolus found in animals.


1. Which part of the cell contains genetic materials?

Ans. Nucleus

Reason: The nucleus contains DNA, the genetic code of every living being, while the nucleolus only contains RNA. The nucleus is responsible for inheritance. Extra-chromosomal material is also present in mitochondria and plastids.

2. Which cellular part constructs ribosomal subunits?

Answer: Nucleolus

Reason: The nucleolus is present inside the eukaryotic nucleus. It is responsible for creating and synthesizing rRNA and the assembly of rRNA with ribosomal proteins, to form ribosomes.

3. Is a nucleolus an organelle?

Although a nucleolus lacks the characteristics of other organelles, it is still an organelle. However, it does not contain a lipid bilayer membrane.

4. What happens if a cell does not have a nucleolus?

Nucleolus is the site for ribosome production. Without nucleolus ribosomes won’t be produced and protein synthesis will not take place.

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