What is a Nucleolus Function?
Nucleolus Function: The nucleolus is a round body located inside the nucleus of a eukaryotic cell. It is not surrounded by a membrane but sits in the nucleus. The nucleolus makes ribosomal subunits from proteins and ribosomal RNA, also known as rRNA. It then sends the subunits out to the rest of the cell where they combine into complete ribosomes. Ribosomes make proteins; therefore, the nucleolus plays a vital role in making proteins in the cell.
The nucleolus is considered as the brain of the nucleus. It occupies around 25% of the volume of the nucleus. It is mainly involved in the production of subunits which then together form ribosomes. Therefore, nucleolus plays an important role in protein synthesis and the production of ribosomes in eukaryotic cells.
What is the function of nucleolus?
Nucleolus helps in protein synthesis and production of the ribosome in the cells.
Where is the nucleolus located in the cell?
The nucleolus is located inside the nucleus of the eukaryotic cell. It is surrounded by a membrane inside the nucleus.
What does the nucleolus contain?
The nucleolus contains DNA, RNA and proteins. It is a ribosome factory. Cells from other species often have multiple nucleoli.
Is nucleolus an organelle?
Nucleolus is not an organelle because it is devoid of a lipid membrane. It is one of the non-membrane bound organelles present in the cell.
What would happen if there is no nucleolus in the cell?
If the nucleolus didn’t exist, there would be no production of ribosomes and there would be no synthesis of proteins.
What Is The Function Of The 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.
Nucleolus Function In Animal Cell
In eukaryotic cells, nucleolus has a well-ordered structure with four main ultrastructural components. The components can be further identified as:
- Fibrillar Centers: It is the place where the ribosomal proteins are formed.
- Granular Components: Before ribosomes are formed, these components have rRNA that binds to ribosomal proteins.
- Dense Fibrillar Components: It has new transcribed RNA which connects to the ribosomal proteins.
- Nucleolar vacuoles: It is present only in Plant cell.
The ultrastructure of the nucleolus can be easily visualized through an electron microscope. The arrangement of the nucleolus within the cell can be clearly studied by the techniques – fluorescent recovery after photobleaching and fluorescent protein tagging.
The nucleolus of several plant species has very high concentrations of iron in contrast to the human and animal cell nucleolus.
Nucleolus Function In Plant Cell
Estable and Sotelo (1951) described the structure of a nucleolus under the light microscope. According to them, nucleolus consists of a continuous coiled filament called the nucleolonema embedded in a homogenous matrix, the pars amorpha. The first description of nucleolar ultra structure was given by Borysko and Bang (1951) and Bernhard (1952).
They described two main nucleolar components, a filamentous one corresponding to the nucleolonema and a homogenous one corresponding to the pars amorpha (matrix).
Later on, Gonzales- Remirez (1961) and Izard & Bernhard (1962) demonstrated that the nucleolonema consists of a spongy net work in place of a continuous filament. The ultra structure of the nucleolus have been reviewed by Day (1968), Bernhard and Granboulan (1968) and Bush and Smetana (1970).
What Is The Main Function Of The Nucleolus?
(i) Ribosome formation or biogenesis of ribosomes.
(ii) Synthesis and storage of RNA:
It produces 70-90% of cellular RNA in many cells. It is source of RNA. The chromatin in nucleolus contains genes or ribosomal DNA (rDNA) for coding ribosomal RNA. Chromatin containing DNA gives rise to fibrils containing RNA. Granules containing RNA already produces ribosomes.
(iii) Protein synthesis:
Maggis (1960) and others have suggested that protein synthesis takes place in nucleolus. Other studies confirm the above views. In eukaryotes the gene coding for RNA contains a chain of at-least 100-1000 repeating copies of DNA. This DNA is given off from the chromosomal fibre in the forms of loops. The DNA loops are associated with proteins to form nucleoli.
The DNA seems as a template for 45S rRNA. Half the 45S rRNA is broken down to form 28S and 18S RNA. The other half is broken down further to nucleotide level. Within the nucleolus the 28S rRNA combines with proteins made in cytoplasm to form the 60S ribosomal sub-unit. The 18S rRNA also associates with proteins to form the 40 S subunit of the ribosome.