The Nucleus- controlling centre or Brain of a cell

In this article we are going to know about the nucleus and why it is called the control Centre or brain of the cell some of you might have started thinking does cell also contains brain? But yes, cell also has its own controlling centre that controls the cell and perform all the necessary functions to keep a cell in living state.

NUCLUES - BRAIN OF A CELL

Nucleus is the controlling Centre or brain of a cell in Eukaryotic cell. Nucleus contain most of the genetic material of the cell and0 this genetic material is called chromatin. Most of Eukaryotic cell have one nucleus called Uni nucleated but some may have more than one nucleus called multi nucleated however some cells lack nucleus called a nucleated.
When nucleus is in non dividing face it contains four components nuclear envelope, nucleolus, nuclear matrix and chromatin.

Nuclear envelope:-

As nucleus is a double membrane organelle it consist to two membranes, inner one is called inner membrane which is directly in connection with nucleoplasm or nuclear matrix and the outer one is called outer membrane which is connected to endoplasmic reticulum. The space between the inner and outer nuclear membrane is called Perinuclear space.
The nuclear envelope contains nuclear pore for transportation of macromolecule in an out of the nucleus. Each nuclear pore is made up of large different protein complexes called as nuclear pore complex. These large proteins which makes the nuclear pore Complex are called nucleoporines. These nucleoporins are multiple copies of about 30 different type of proteins.
Nuclear pore complex is a cylindrical structure with octagonal symmetry. The nuclear pore complex is made up of Central pore, luminal ring, cytoplasmic rings, nuclear rings and nuclear basket.

1) Central pore- composed of multiple copies of nucleoporin proteins, which are arranged in a ring-like structure with an inner diameter of about 9 nanometers.

It has FG repeats that line the central pore. This repeats are rich in phenylalanine and glycine. Forms hydrogen like meshwork lines.
It is a selective barrier and regulate the transportation of molecules through pores.

2) luminal rings- it is a spoke assembly of 8 angular units made up of a complex of three nucleoporins (Nup107, Nup160, and Nup133) and serves as a scaffold for the assembly of other nucleoporins. It act as a diffusion barrier that prevents the unregulated passage of molecules through the NPC.

3) cytoplasmic ring- it is located on the cytoplasmic side of the nuclear envelope and is made up of several nucleoporins. It plays an important role in the transport of molecules between the nucleus and cytoplasm. It serves as a docking site for transport receptors, the receptors recognize this site and bind to specific cargo molecules and facilitate their transport through the NPC.

4) nuclear ring- is a protein structure located on the nuclear side of the nuclear envelope. It serves as a selective barrier for the transport of molecules between the nucleus and the cytoplasm. It serves as a docking site for transport receptors, the receptors recognize this site and bind to specific cargo molecules and facilitate their transport through the NPC. It also interacts with other cellular structures, such as the nuclear lamina and the chromatin.

5) nuclear basket- it is located on the nuclear side of the NPC. It is made up of several filamentous extensions that protrude into the nucleoplasm and are anchored to the NPC. It plays an important role in the regulation of nucleocytoplasmic transport. It also interacts with other cellular structures, such as the nuclear lamina and chromatin, to help maintain the structural integrity of the NPC.

 

 READ MORE: Cell organelles

B) Nuclear matrix-

It is also called nucleoplasm. It is a transparent semifluid and colloidal substance which contains nuclear lamina, a network like internal nuclear matrix.

1) Nuclear lamina- it is a network of intermediate filaments lies on inner side of inner nuclear membrane and it is made up of lamin protein.

The nuclear lamina give shape and stability to the nuclear envelope. It links the internal nuclear Matrix to the nuclear membrane. It also help in regulating important nuclear functions such as DNA replication, transcription, and DNA repair.

2) Internal nuclear matrix- it is a liquid filled inside the nucleus which contains network of RNA and proteins distributed throughout the nucleoplasm.The internal nuclear matrix plays a critical role in organizing the chromatin and regulating gene expression.

C) Nucleolus- 

it is spherical shaped non membraneous dynamic body. It consist of three major reasons fibriller centre, dense fibrillar components and granular regions.

1) Fibrillar centers- contains r-RNA genes in the form of partially condense chromatin. It has DNA, RNA and proteins. Here r- DNA is converted into pre r-rna.

2) Dense fibrillar components- it is a site of processing of Pre r-rna into m r-RNA. It contains RNA and proteins.

3) Granular regions- it is the outermost region where the Assembly of ribosomal units take place. It has region of RNA + proteins.

It is a site of transcription of ribosomal RNA and assembly of ribosomes. Nucleolus is produced by a nucleolus organising region(NOR) of a chromosome.

NOR is this specific region of chromosome contains genes for RNA synthesis and this genes are transcribed by RNA polymerase-1 into Pre r- RNA.
This nascent pre-rRNA processed means undergone cleavage and base modifications to form mature r-RNA. after this the assembly of these RNAs with the ribosomal proteins present in nucleolus generates small and large ribosomal subunits, the pass Into cytoplasm.

In human 5 chromosomes contain NORs which identified as secondary constrictions on metaphase chromosomes.

D) Chromatin-

 it is a unwind network of nucleoprotein fibres present in interface nucleus. Chromatin and chromosomes are basically the same things but the difference is that chromatin is less condensed while chromosome is highly condensed DNA. Chromatin is essentially composed of DNA and basic proteins called histones, it also contains RNA and some non histone proteins. Histone proteins help in packaging the DNA to form a compact structure called chromosome.

Inating two types of regions can be observed heterochromatic region and Euchromatin region.

1) Heterochromatin region- This is a region which is darkly stained and it is genetically inactive means transcription does not take place in this region because of highly condense reason with tight packed DNA.

Euchromatin region- This is a region which is lightly stained and it is genetically inactive means transcription takes place in this region because of loose Packaging of DNA.

Transcriptionally active chromatin is found at the periphery whereas transcriptionally in active chromatin tends to be located more at centre.

CONCLUSIONS-

1) Nucleus is the control centre of the eukaryotic cell.

2) Nucleus consists of 4 component as nuclear envelope, nuclear matrix, nucleolus and chromatins.

3) nuclear envelope has two membrane as inner membrane and outer membrane and these membrane fuse at nuclear pore.

4) nuclear pore complex is a cylindrical and octagonal symmetry structure it consist of Central pore, luminal rings, cytoplasmic rings, nuclear rings and nuclear basket.

5) nucleoplasm is a transparent semifluid and collodial substance which fills the nucleus. It consist of nuclear lamina and a network like internal nuclear matrix.

6) chromatin and chromosomes are basically the same things the difference is that chromatin is less condense and chromosomes are highly condense DNA.

7) chromatin has two types of regions first is heterochromatin region and other one is Eu- chromatin region.

FAQ-

Ques-1 what is nucleus and its functions?
Ans- nucleus is a double membrane organelle which is a control centre of a cell. Nucleus consists of nuclear envelope, nucleoplasm, nucleolus and chromatins. DNA replication, transcription and RNA processing takes place within nucleus of a cell.

Ques-2 what is nucleolus?
Ans- nucleolus is spherical structure present in the nucleoplasm which is non membrane bound structure and it is the site for ribosomal RNA synthesis and ribosomal assembly.

Ques-3 who discovered nucleus?
Ans- nucleus was first discovered by Robert Brown.

Ques-4 what is the difference between chromatin and chromosome?
Ans- chromatin and chromosome basically are the same thing but the difference is that chromatin is less condensed while the chromosomes are highly condense DNA.

Ques-5 how is chromatin formed?
Ans- chromatin is formed by the wrapping of DNA on core histone proteins. This wrapping held together by H1 histone protein also called as linker protein. The 8 histone proteins which combined to form histone Octomer. This whole structure is called as nucleosome.