Structure of cell nucleus


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This subject focuses on “Fundamental Biology and Physiology “it is very important for a person to have full detailed idea about the nucleus and its functions. The subject core idea is been developed and related to the Nucleus. What is Nucleus? In very simple terms Nucleus keeps hereditary information and is control centre of cell by regulating cell activities. It keeps the DNA and helps to keep all the things that a cell really needs to survive. In short it acts as a “brain”.

Cell's genetic materials are been contained in a nucleus with properly organised as in terms of long linear DNA molecules with various kinds of proteins and hence to form chromosome. Nucleus is the typically the most prominent organelle in a cell. The nucleus is usually spherical or oral in shape with an average circular diameter of 5 µm. Nucleus really occupies its primary position at the centre of the cell. Excluding the exception, cells have only a single nucleus. The nucleus envelope has 2 membranes concentric to each other encloses the entire organelle which have function of separating surrounding cytoplasm from the nuclear contents. These two membranes are been separated by about 20 to 40 nm. In interval time, these membranes come close to each other and form nuclear pores and they consist of protein complexes. As for a reason that the nuclear membrane is practically impermeable to most molecules, for the movement of the molecules across the envelope, the pores are been required. The larger molecules like proteins are carefully controlled when they move and use an active transport regulated by carrier proteins.

Inside the nucleus, it does not contain any kind of bounded membrane and contains are not been uniform. The nucleolus, which is the main site where the ribosomal RNA synthesis are found; and nucleoplasmic fibrils and granules, part of which are involved in processing and transport of messenger RNA out of nucleus. This constituents of the nucleus which are been contained in the whole frame which is called as nuclear matrix.

Structure of cell nucleus

In animal body, nucleus is the largest cellular organelle. Practically, Nucleus occupies like around 10% of the total cell volume. Nucleoplasm is the fluid (viscous) found in the nucleus and is same in the composition to the cytosol which is found in the exterior of the nucleus. It appears as a rough, dense spherical organelle.

As been discussed above the structure of the nucleus is been enveloped by membrane consisting of 2 cellular layers. They are arranged concentric to each other. The cellular membrane acts as a barrier and helps to prevent the macromolecules from diffusing freely between nucleoplasm and cytoplasm. Nucleus pores provide aqueous streams throughout the envelope which are mainly composed of the multiple proteins, which are all together referred as nucleoporins. The size of the pore is around 100 nm but it only allows about 9 nm wide gap through which the molecule's free diffusion take place. The nucleus is a very typical kind of mammalian cell consisting of around 3000 to 4000 pores covering throughout the envelope.

As we can see the above figure which is completely detailed figure showing all the different parts of a cell nucleus including the lysosomes, vesicles, golgi complex, plasma membrane and many more parts. The interpretive drawing shows the nuclear envelope of two parallel membranes, which is perforated by nuclear pores. Complex of proteins is been surrounded by each pore.

In animal cells, the nucleus is provided with mechanical support by two networks of intermediate filaments: the nuclear lamina forms an organic meshwork on internal face of the envelope, while cytosolic face of the envelope becomes the less organised support. Structural support is given by both the systems for the nuclear envelope and anchoring sites for chromosomes and nuclear pores. Lamin proteins are mostly there in nuclear lamina. Like other proteins, lamins are also synthesised in cytoplasm and transported to the interior of the nucleus, in which they are been assembled. After the assembly they are been incorporated into the networks which are existing in the nuclear lamina. Nucleoplasm is the place where the lamins are been found and they form another regular structure. The lamin structures which do make up the veil blind chromatic and disrupting their structure inhibits transcription of protein-coding genes.

Function of cell nucleus

Focussing at the cell's nucleus functions, basically the hereditary characteristics of the organism is been controlled by it and is protein synthesis is mainly accountable by it. Cell growth, cell devision and differentiation are the other major function of the cell nucleus. The primary function of the cell nucleus is to control and regulate the gene expression and during the cell cycle, mediate and replicate the DNA.

The various function carried of the nucleus of a cell are as mentioned below:

§ The hereditary materials are been stored; Long and thin DNA strands (deoxyribonucleic acid), commonly known as chromatins, which is the type of genes

§ The various Proteins and RNA (Ribonucleic acid) is stored in the nucleus

§ Transcription is been found in the nucleus where the messenger RNA are been developed for the protein synthesis

§ In between the nucleus and other cell, the exchange of hereditary molecules takes place (DNA and RNA)

§ The chromatins are been arranged in the chromosomes during the cell division

§ In the nucleus, ribosomes (protein factories) are produced

§ Energy molecules and Selective transportation are been selectively transported through help of nuclear pores. [1]





Large structure surrounded by double membrane; contains nucleolus and chromosomes

Information in DNA in transcribed in RNA synthesis; specifies cellular proteins


Granular body within nucleus; consists of RNA and protein

Site of ribosomal RNA synthesis; ribosome subunit assembly


Composed of a complex of DNA and protein known as chromatin; condense during cell division, becoming visible visible as rodlike chromosomes

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