Cell nucleus, functions, structure and composition

Cell nucleus, functions, structure and composition

The cell nucleus is a fundamental compartment of eukaryotic cells. It is the most visible structure of this type of cell and has the genetic material. It directs all cellular processes: it contains all the instructions encoded in DNA to perform the necessary reactions. It is involved in the processes of cell division.

All eukaryotic cells have a nucleus, except for specific examples, such as mature red blood cells (erythrocytes) in mammals and phloem cells in plants. There are also cells with more than one nucleus, such as some muscle cells, hepatocytes and neurons.


The nucleus was discovered in 1802 by Franz Bauer; However, in 1830, the scientist Robert Brown also observed this structure and became popular as its main discoverer. Due to its large size, it can be clearly seen under a microscope. In addition, it is a light coloring structure.

The nucleus is not a homogeneous, static spherical entity with dispersed DNA. It is a complex and complex structure, with different components and components inside. In addition, it is dynamic and constantly changing throughout the cell cycle.

Read : Kingdom Animalia

characteristics of Nucleus

The nucleus is the main structure that allows the differentiation between eukaryotic and prokaryotic cells. It is the largest cell compartment. In general, the nucleus is close to the center of the cell, but there are exceptions, such as plasma cells and epithelial cells.

It is a sphere-shaped organelle with an average diameter of about 5 μm, but can reach 12 μm, depending on the cell type. They can occupy about 10% of the total animal cell volume.

It has a nuclear shell made up of two membranes that separate it from the cytoplasm. The genetic material is organized together with the proteins inside.

Despite the fact that inside the nucleus there are no other membranous sub-compartments, if one can distinguish a number of components or regions within the structure that have specific functions.

Definition of Nucleus

A cell nucleus is known as a membranous organelle that is found inside eukaryotic cells exclusively, and that contains most of the genetic material of the cell, organized in DNA macromolecules called chromosomes, inside which are the genes .

Understanding the nucleus is one of the three main parts of the nucleus cell, with part of an organelle found in eukaryotic organisms. As the nucleus contains various genetic material such as DNA, chromosomes and proteins, the nucleus can also be seen easily using a light microscope without the aid of chemical dyes. Where every cell always has a nucleus except a certain type, which sometimes has more than one nucleus in the cell.

History of the discovery of the Nucleus

According to experts the cell nucleus was the first organelle to be found and examined directly, the cell nucleus was also described by Franz Bauer in 1802.

The cell nucleus was first described by antonie van leeuwenhoek, who at the time was examining the cell nucleus contained in salmon red blood cells.

In 1831, a Scottish botanist named robert brown explained the description of the cell nucleus in more detail.

He examined the cell nucleus in the epidermal cells of orchids, he could not explain the function of the cell nucleus from this study.

In 1838 Matthias Schleiden stated that the cell nucleus plays a role in cell formation, which is then called the cytoblast which means formation in cells.

Hertwig also examined animals such as mollusks and amphibians, in 1884, Eduard Strasburger also received the same research results on plants.

Cell nucleus, functions, structure and composition

Structure of the nucleus

The nucleus is the largest organelle in the cell. The nucleus appears to be a dense spherical organelle. It occupies about 10% of the total cell volume. In mammalian cells, the average diameter of the nucleus is approximately 6 microns. A semi-fluid matrix nucleoplasm is seen within the nucleus which is a viscous fluid and is similar to the composition of the cytoplasm.
The following are some of the nucleus structures, including:

1. Nuclear Membrane
2. Nuclear pore
3. Nucleolus
4. Chromosomes

1. Nuclear Membrane Structure

  1. The nuclear envelope is also known as the nuclear membrane.
  2. It consists of two membranes of the outer membrane and the inner membrane.
  3. The outer membrane of the nucleus is continuous with the membrane of the rough endoplasmic reticulum.
  4. The space between these layers is known as the perinuclear space.
  5. The nuclear envelope encloses the nucleus and separates the cell's genetic material from the cell's cytoplasm.
  6. It also serves as a barrier to prevent the passage of macromolecules freely between the nucleoplasm and the cytoplasm.
  7. The structure of the nuclear membrane is a double phospholipid membrane that is covered by the cell body and acts as a divider between the cell nucleus and the cytoplasm of the cell.
  8. Like cell membranes in nuclear membranes also play a role in regulating the process of replacing fuel inside the cell and outside the cell nucleus.

Here are the core parts of the membrane, including:

1. Outer membrane is usually called an organelle that spreads on the ribosome wall.

2. Perinuclear space : Perinuclear space is the existence between the core membrane space and the initial membrane space.

2. Nucleoplasm : Nucleoplasmas are called solid liquids in the cell nucleus, which include interests in nucleoplasms such as gramnula, chromatin, and compounds in chemistry.

3. Nucleoli or Child Nucleus : Nuclear nucleus is one of the nucleus nucleus cells consisting of phosphoprotein, DNA, orthosfate, and various kinds of enzymes that are protected on the membrane.

Then there is the rRNA / ribosome with the cell nucleus in a fixed structure after work.

4. Chromatin : The chromatin in interphase appears as granules scattered throughout the nucleus without chromosomal threads, otherwise if the nucleus of the cell is posed with, the chromatin beads are invisible and chromosomal threads appear.

Because it contains this komatin, the nucleus acts as genetic information and controls all cell activity.

Control of all cell activities, because in the nucleus that there is chromatin in it, it is through DNA that proteins are synthesized with the help of RNA and enzymes.

Protein is a molecule that is very important for our cells and body because enzymes, hormones, and antibodies need protein.

5. Nucleic Acid :  Nucleic acid A DNA dioxyribose acid which usually joins in the nucleus and will form a protein called nucleuprotein.

Then there will be some amount of nucleus DNA in the content of salamanders which is more mammalian DNA.

6. Nucleus Protein : The types of nucleus proteins are protamin and histone, which are the types of proteins in the nucleus and there are other acidic proteins, such as non-histone proteins and nuclear enzymes.

7. Mineral Salt : Mineral salts that contain a number of precursor cofactors and minerals NAD, ATP and Acetil CoA, and will produce analyzes on calcium and magnesium.

8. DNA : DNA molecules are known as genetic material that stores all important information about all cell activities that must be carried out to live life.

DNA or deoxyribonucleic acid is compared to large formulations that contain important books or genes and are stored properly in the cell nucleus.

DNA molecules have a structure in the form of two double strands, each of which consists of polynucleutides in a series of nucleutides in the form of deoxyribonucleutides.

Each nucleotide molecule consists of three groups, namely pentose sugar groups in the form of deoxybose, phosphate groups and alkaline nitrogen-containing groups

9. RNA : Ribonucleic acid RNA or ribonucleic acid is a macromolecule that acts as a store and distributor of genetic information, RNA as a store of genetic information.

For example:
  1. Regarding viral genetic material, specifically retroviruses, RNA as a supplier of genetic information, is a translation process for protein synthesis.
  2. RNA can also act as an enzyme or ribozyme that can track the formation of RNA itself or other RNA molecules.

10. RNA structure : RNA is a single chain of polynucleotides with each ribonucleotide consisting of several groups of molecules

For example nitrogen-based carbon which consists of purines that are identical with different DNA and pyrimidines, namely cytosine and uracic phosphate groups

2. Nuclear pore

  1. The nuclear envelope is pierced with numerous pores called nuclear pores.
  2. Nuclear pores are made up of many proteins known as nucleoproteins.
  3. Nuclear pores regulate the passage of molecules between the nucleus and the cytoplasm.
  4. The pores also allow the passage of molecules only about 9nm wide. The larger molecules are transferred through active transport.
  5. Molecules like DNA and RNA are allowed in the nucleus. But energy molecules (ATP), water, and ions are freely allowed.

Read : Animal & plant Cell 

3. Nucleolus

  1. The nucleolus is not surrounded by a membrane, it is a densely stained structure found in the nucleus.
  2. Nucleoli form around nuclear organizing regions.
  3. It synthesizes and assembles ribosomes and r RNA
  4. The number of nucleoli is different from one species to another, but within a species the number is fixed.
  5. During cell division, the nucleolus disappears.
  6. Studies suggest that the nucleolus may be involved in cellular aging and senescence.

4. Chromosomes

  1. The cell nucleus contains most of the genetic material of the cells in the form of multiple linear DNA molecules.
  2. These DNA molecules are organized into structures called chromosomes.
  3. Chromosomes are the filaments of genetic material (DNA and proteins) that appear in the cell when it is dividing. 
  4. DNA molecules are in complex with a wide variety of proteins (histones) that make up the chromosome.
  5. In the cell they organize into a DNA-protein complex known as chromatin.
  6. Chromatin is condensed in order to distribute the genetic information of the stem cell between the two daughter cells.
  7. During cell division, chromatin forms well-defined chromosomes.
  8. Genes within chromosomes consist of the nuclear genome of cells.
  9. The cell's mitochondria also contain a small fraction of genes.
  10. Human cells have almost 6 feet of DNA, which is divided into 46 individual molecules.

A chromosome has the following structure:
  1. Two sister chromatids. The DNA of each chromatid is identical, which is why they are called sister chromatids.
  2. Centromere. Place where the two sister chromatids meet.
  3. Arms. Each chromatid is made up of two arms that can have the same or different length, depending on the chromosome. Each arm is the part of the chromatid that goes from the centromere to the telomere.
  4. Telomeres. They are the ends of the arms.

Cell nucleus, functions, structure

Types of Necleus 

The following are 2 types of nucleus that need to be known, including:

1. Types of Mononucleate Cells
As the name mono means one, hence mononucleate cells are cells that only have one cell nucleus, most animal and plant cells only have one cell nucleus.

2. Multinucleate Cell Types
Multi nucleus cells are cells with more than one nucleus, for cells that are basically two cells called binucleate cells, whereas cells with more than two nuclei are called polynucleate cells.

Functions of Nucleus 

Here are some functions in the nucleus, including:

1. To Store Genetic Information
One of the functions of the nucleus is to store genetic information, which is due to the presence of a nuclear membrane in protecting the DNA it contains.

2. As a Replication and Transcription Place
The function of the nucleus is also a function that is protected by the nucleus or cell, that is, as DNA displayed in the mitotic process which will begin after DNA replication.

3. Cell Growth
The function of the cell growth nucleus is to control cell activity, but it also functions as a nucleus to regulate cell growth in the body.

As cells are divided to expand, even cells that do not divide have control over the cell nucleus.

4. Control Metabolism
Controlling metabolism is based on the process in which proteins are produced, this process also occurs due to transcription and translation in the cell nucleus.

In short, the important functions of the nucleus are:
  1. Nucleus contains and stores chromosomes that carry genetic information (genes), especially during reproduction processes such as mitosis.
  2. The nucleus regulates genes into specific chromosomes, which allows cell division and facilitates the work of transcribing its contents.
  3. The nucleus allows the transport of molecules between the nucleus and cytoplasm, selectively according to their size.
  4. The nucleus produces messenger RNA (mRNA) from the DNA matrix, which transports genetic sequences to the cytoplasm and functions as a matrix for protein synthesis carried out in cells.
  5. The nucleus produces ribosomes which are very necessary to make ribosomal RNA (rRNA).

Read : Lysosomes

Frequenty Asked Questions

1. What is the nucleus easy defination?
Answer : A cell nucleus is known as a membranous organelle that is found inside eukaryotic cells exclusively, and that contains most of the genetic material of the cell, organized in DNA macromolecules called chromosomes, inside which are the genes .

2. What does a nucleus look like?
Answer : When you see Nucleus under Microscope it look like a The interphase nucleus a DNA is in the form of chromatin, dispersed throughout the cytoplasm, forming a network. The interface is a very important stage of the cell life cycle, since it covers 90% of the time. It is when DNA duplication and RNA synthesis occurs, that once transported to the cytoplasm they will be in charge of directing the synthesis of enzymes and proteins.

3. Where is a nucleus located?
Answer : The Cell nucleus Contain genetic information of an organism. In animal cell, the nucleus is located in the central region of the cell.

4. How is a nucleus formed?
Answer : The nucleus of a cell is formed from the nucleus of the cell that divided to form it by the process of Karyokinesis. Each cell's nucleus divides into two nuclei every time the cell divides.

5. Which cell has no nucleus?
Answer : prokaryotic cells
Cells that lack a nucleus are called prokaryotic cells and we define these cells as cells that do not have membrane-bound organelles like Mitochondria, ribosomes nucleus etc.

6. Why is the nucleus so important?
Answer : Because nucleus is the most important organelle in the cell. It contains the genetic material of organism, the DNA, which is responsible for controlling and directing all the activities of the cell. All the RNAs needed for the cell are synthesised in the nucleus.

7. Why is DNA stored in the nucleus?
Answer : In organisms called eukaryotes, DNA is found inside a special area of the cell called the nucleus. Because the cell is very small, and because organisms have many DNA molecules per cell, each DNA molecule must be tightly packaged.

8. What is nucleus and nuclei?
Answer : Nucleus is just the singular form and Nuclei is the plural form. Nucleus (pl: nuclei) is a Latin word for the seed inside a fruit. It may refer to: Atomic nucleus, the very dense central region of an atom. Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA.

9. What is the function of the nucleus 
Answer :
  1. Controls the hereditary characteristics of an organism.
  2. It is responsible for protein synthesis, cell division, growth and differentiation.
  3. Stores hereditary material in the form of deoxyribonucleic acid (DNA) chains.
  4. It helps in the exchange of DNA and RNA (hereditary materials) between the nucleus and the rest of the cell.
  5. The nucleolus produces ribosomes, known as protein factories.
  6. Regulates the integrity of genes and gene expression.

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