What Is A Nucleus – Discovery, Origin, Shape, Size, Structure, Best Functions

What Is A Nucleus | Nucleus Definition Biology | Nucleus Function | Structure Of Nucleus | Nucleus Definition |

What Is A Nucleus

The nucleus is the densest cell of the eukaryotic cell’s protoplasm, surrounded by two single membranes, consisting of almost gallbladder and chromosomes that control all the functions of the cell organelle.

Nucleus Discovery

Robert Brown (1831) first discovered and named the nucleus in the cell of a plant called Tradescantia.

Origin of Nucleus

A new offspring nucleus is formed from the former maternal nucleus. New nuclei are not formed automatically or from other objects.

Location of Nucleus

The nucleus is located in the center of the cell. For metabolism, the nucleus moves towards the circumference of the cell. When the wheat of the plant cell grows, the nucleus moves to the end of the cell.

Number of Nuclei

Usually, there is a nucleus in the cell. The unicellular paramecium contains two nuclei in the liver and cartilage cells of mammals. Many nuclei are found in the bone marrow of Vaucheria algae, Rhizopus fungi, unicellular animals called Opalina, and vertebrates. Many nucleated cells are called syncytial cells or syncitium and many nucleated plant cells are called coenocytes. The nucleus is not found in mature red blood cells of mammals and in the sieve tube of advanced plants.

Shape of Nucleus

The nucleus is usually globose, but it can be oval, elliptical, or spherical. Different white blood cell nuclei have different shapes. The nucleus as a whole has no fixed angle.

Structure Of Nucleus

The nucleus is the largest cell organelle and can be up to 5-25 am in diameter. Cell size depends on the number of chromosomes, metabolism, and cell division. Scientist Hertwig has discovered a formula for the relationship between cell volume and the size of the nucleus. E.g.-

1. Eukaryon – The cell has only one nucleus.
2. Dikaryon or Homokaryon – The cell has two nuclei of the same type.
3. Polykaryon cells have many similar nuclei.
4. Heterokaryon – The cell has two different types of nuclei.
5. Synkaryon – The nuclei of two different cells combine to form a nucleus.
6. Amphinucleus – The nucleus of this cell contains two sets of genomes and the nucleus is therefore found in the diploid body cell.
7. Heminucleus is the only set of genomes here, so it is in the nucleus of haploid and gamete (sperm and ovum).
8. Before the nucleus of the egg and sperm meet during fertilization of the pronucleus.
   The condition is called pronucleus. At this time the nucleus of the sperm is known as the male then nucleus and the nucleus of the ovum is called the female pronucleus.
9. Micronucleus and Macronucleus – The dication cell has two unequal nuclei, the big one is called micronucleus and the sixth one is called micronucleus.

Structure Of Nucleus

1. Nuclear term
2. Nuclear juice or nucleoplasm
3. Chromatin reticulum or nuclear reticulum or chromosome
4. Nucleolus.

Nuclear Membrane

a) The screen that covers the entire nucleus is called the nucleus.

b) Structure

(i) Cytoplasm The nucleoplasm is separated by a membrane.

(ii) Every single membrane is composed of a three-layered protein-lipid-protein (P-L-P) and is 75-90A thick. There is a gap of 100-150 A between two single positions and it is called perinuclear space.

(iii) Something in the outer single position The ribosome sticks, so the term is uneven. The nucleus has a nuclear pore with a diameter of 300-500A and this hole is covered with the proteinous annulus.

(iv) Nucleoplasmin proteins located in the nucleus are used to exchange substances in the nucleus.

c) Function of the nuclear body: (i) Nuclear body protects the objects inside the nucleus. (ii) Provides specific shape of the nucleus. (iii) Regulates the exchange of matter inside and outside the nucleus. (iv) Separates cytoplasm and nucleoplasm.

Nuclear Sap Or Nucleoplasm

Definition: The translucent, tiny granular, slightly acidic, semi-liquid substance inside the nuclear membrane is called nuclear juice or nucleoplasm.

Structure: This fluid contains DNA, RNA, various proteins (histone, protamine, phosphoprotein, etc.), many enzymes (DNA and RNA polymerase, ribonuclease, phosphatase, dipeptides, etc.), co-enzymes, ATP, and various minerals. , Ca, Mg, P), etc. The nucleoplasm contains chromatin lattice and nucleolus.

The function of Nuclear Juice: Nuclear juice acts as the liquid medium of the nucleus.

Nuclear reticulum or chromatin reticulum:

Definition: The structure of the reticulum, which is located in the nucleus juice, is made up of fine fibers made of alkaline pigments, nucleic proteins. The threads are called chromatin threads. These are made up mainly of DNA and histone proteins. In the cell interface phase, the chromatin formulas are reticulated, but in the division phase, they coil and form a clear chromosome. There are two types of chromatin formulas (according to the religion of dyeing), such as heterochromatin and euchromatin.

Heterochromatin: Heterochromatin is the chromatin that is coiled and has a very dark color in both the stable and divisive stages of the cell. Heterochromatin is the inactive component of chromatin, meaning that no genes are present here and no RNA is formed from the DNA of this component, so no protein is available.

Euchromatin: The part of the chromatin lattice that is light in color at the nucleus stage but dark in the split stage is called euchromatin. In the stationary state of the cell, euchromatin is in an undifferentiated or loosely expanded state, but in the fission state, it is in a very patchy state. Euchromatin is the active component of chromatin. This means that this part carries all the genes that carry the characteristics of an organism, RNA is made from the DNA of this part, and proteins are found.

Nucleus Definition Biology

Nucleolus Definition: A nucleus is a small, dense, glabrous, dark-colored object that is found in the nucleus and is found only in the stationary state of the cell. Discovery Fontana (Fontana, 1781) discovered the nucleolus.

But more than one nucleolus is found in different cells, such as lymphocytes, liver cells, etc.

Structure of Nucleus: The nucleolus is composed mainly of RNA and proteins. The four nuclei are seen in the nucleolus-
(i) Amorphous or Amorphous zone – The region forms the nucleolus nucleus and contains granular and fibrillar material.
(ii) Granular zone – The grains of this region is composed of ribonucleic proteins with a diameter of 150-200 A. These are called ribosomes of the nucleus and these
Plays a special role in the formation of ribosomes in the cytoplasm.
(iii) Fibrillar zone This part is made up of fine ribonucleic protein formula and this 50-80 A long filament is called nucleonema.
(iv) Chromatin Zone – The chromatin that surrounds the nucleolus along the perimeter is called the perinucleolar chromatin and the part of the chromatin that enters the nucleolus is called the internuclear (chromatin).

(c) Functions of Nucleolus: Rhizome RNA (rRNA) is formed from the DNA of the chromatin region of the nucleolus. Thus the nucleolus mainly produces ribosomal RNA and plays a special role in ribosome and protein synthesis.

function of nucleus

1. The nucleus is the heart of the cell which controls all the biological functions of the cell, hence it is called “Brain of the cell”.
2. The DNA present in the nucleus carries all the properties and properties of the cell from one generation to another.
3. RNA and proteins are synthesized from the nucleus.
4. The nucleus plays a major role in cell division.

Nucleus Definition Biology

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