The name Nucleus is derived from the Latin word Nux-nut. The dense, opaque and spherical organelle located in the protoplasm of the cell which carries the genetic material and controls the vital functions of the cell is called the nucleus. It is also called the nucleus, nucleus and brain of the cell. It is the largest cell organelle.
Dutch scientist Anthony von Leeuwenhoek was the first to observe the lumen or nucleus in the red blood cells of salmon. In 1831, Robert Brown discovered the nucleus from Rasna leaves. In 1882, scientist Strasburger gave the idea of nucleoplasm. In 1953, scientist J. Hammerling sheds light on the function of hereditary characteristics of the nucleus.
Normally each cell has a nucleus. However, cells of Vaucheria, Botrydium, Sphaeroplea, Penicillium, Opalina, Osteoclasts and Paramecium are more numerous. Multinucleated plant cells are called sinocytes. Animal cells with multiple nuclei are called syncytium. Stem cells, stem cells and mammalian red blood cells (except camels) do not have a nucleus. Nucleus may occupy 10-15% of cell space. About 90% of sperm are nuclei.
The nucleus is usually round. But can be ellipsoidal, flattened, fusiform (rounded), toothed etc. Spherical nucleus is one micron in diameter. Cells with more cytoplasm have larger nuclei and cells with less cytoplasm have smaller nuclei.
Structure of Nucleus
The parts of the nucleus are:
- Nuclear membrane or envelope: The membrane that covers the nucleus is called nuclear membrane or nuclear membrane. It is called the envelope, nucleolemma or karyotheca. The nuclear membrane is bilayered. Outer cover and inner cover. It is composed of phospholipids. The space between the two envelopes is called the perinuclear space. The distance between perinuclear spaces is 10-15 nm. Blisters originating from within the nuclear envelope are called nuclear blisters. The nuclear membrane contains nucleoplasmin. Nucleoplasmin mediates the exchange of various substances.
Function: The main function of the envelope is to separate the nucleoplasm, nucleolus and chromatin from the cytoplasm. Endoplasmic reticulum keeps the nucleus connected. Necessary materials transport from inside to outside and from outside to inside.
- Nuclear Pore: The nuclear envelope consists of octagonal pores. These pores are called nuclear pores. Nuclear membrane has 300 pores. The number of nuclear pores per square micrometer is 40-145. The hole-to-hole distance is 1500 Å. The diameter of each pore is 9 nm. The pores are constricted and expanded by a protein network.
The nuclear pore contains the annulus. The annulus contains 8 granular edge proteins. Peripheral proteins are linked by spokes. At the center of the nuclear pore is a large protein called a transporter. The transporter is attached to the envelope by anchor proteins. Proteins can consist of subunits and fibers. Inside the nucleus is a fibrous cage. Proteins are attached to the fiber cage. Peripheral proteins associate with the transporter to form a wheel-like structure.
Function: It maintains contact with the cytoplasm and transports materials. The product passes through the nuclear pores into the cytoplasm.
- Nucleoplasm: The clear, granular and jelly-like semi-fluid substance inside the nuclear membrane is called nucleoplasm or karyolymph. It is called protoplasmic juice or nucleo juice of nucleus. It is mainly composed of proteins. It contains DNA polymerase, RNA polymerase, phosphoprotein, histone protein, nucleotide triphosphatase, nucleoside phosphorylase, kinase, dehydrogenase, endonuclease, lipid and mineral salts.
Function: It contains nucleolus and chromosomes. Helps in various biological functions. The nucleoplasm serves as the main site of enzyme activity.
- Nucleolus: The dense, bright and spherical material seen inside the nucleus is called nucleolus. Each nucleolus consists of three parts. Pars Amorpha, Nucleonima and Matrika. The surrounding part of the nucleolus is called pars amorpha, the central part is called nucleonema and the liquid part inside is called matrix. It is attached to a chromosome called the organizer. The location of the chromosome where the nucleolus is attached is called the SAT or satellite. Nucleolus contains DNA, RNA, proteins, lipids, enzymes, phosphorus, sulphur, potassium etc. In 1781, the scientist Felice Fontana first observed the nucleolus. Nucleolus was named by Bowman in 1840. The SAT gene located on the satellite of the chromosome plays a direct role in the production of nucleolus. Cells that do not synthesize proteins do not have a nucleolus. Spermatozoa, red blood cells and white blood cells do not contain nucleolus.
Function: Nucleolus synthesizes different types of RNA. It synthesizes and stores proteins. It acts as a storehouse of nucleotides. It creates ribosomes.
- Chromatin: The fine thread-like structure found inside the nucleus is called nuclear reticulum or chromatin fibers. The unit of chromatin is the nucleosome. A necklace-like structure formed by enclosing histone proteins is called a nucleosome. Each human cell contains about 3×107 nucleosomes. It is called chromatin because it contains some basic color (fluorescent color) when the cell is stained. Chromatin is characterized by two regions due to its ability to absorb color. Euchromatin and Heterochromatin. The darker colored denser region of chromatin is called heterochromatin and the lighter colored less dense region is called euchromatin. Chromatin is divided into thick and short sections called chromosomes. Each chromatin contains DNA, histone proteins and non-histone proteins.
Function: Chromatin contains DNA. It acts as a carrier and carrier of hereditary characteristics. It plays a key role in the variation and mutation of organisms.
Function of Nucleus
- Biological function: The nucleus is called the brain of the cell. It controls all biological functions of cells.
- Heredity: DNA molecules present in chromosomes control the heredity of organisms.
- Protein synthesis: Nucleolus forms ribosomes and ribosomes make proteins.
- Metabolism: Nucleus is the organelle that regulates cell metabolism.
- Regulation of enzyme activity: Nucleoplasm serves as the main site of enzyme activity.
- Variation and mutation: It causes variation and mutation in organisms. As a result, evolution takes place in the living world.
- Metabolism: The nuclear membrane acts as a medium of exchange. It exchanges essential substances between cytoplasm and nucleoplasm.
- Cell division: It plays an important role in cell division.
- Differentiation: Nucleus controls cell differentiation during embryonic development.
- Shape the cell: The nuclear membrane forms the various structural components of the cytoplasm. These elements help in cell shape.
Role of nucleus in the growth of organisms
- The nucleus is called the brain of the cell. It controls all biological functions of cells. It also regulates the growth of organisms.
- Nucleolus forms ribosomes and ribosomes make proteins. These proteins make up the organism’s body.
- The nucleus is the cell’s metabolic control organelle. It boosts the metabolism of organisms and helps in growth.
- The nucleoplasm serves as the main site of enzyme activity. Nucleus promotes growth of organisms by regulating enzyme activity.
- The nucleus carries out the exchange of essential substances. These substances help in cell growth.
- Nucleus controls cell mitosis cell division. The number of body cells increases in the process of mitosis. Physical growth of the organism occurs when the number of body cells increases.
Role of nucleus in reproduction of organisms
- Nucleus controls cell mitosis cell division. Genitalia of multicellular organisms are formed in the process of mitosis. Participates in reproductive work.
- Nucleus controls cell meiosis cell division. In the process of meiosis, sperm and ovum are formed from the generative mother cells. Participates in sperm and egg production.
- Nucleus Cell Mitosis causes cell division. Mitosis plays an important role in cell division. Roots are produced by vegetative propagation by cuttings, layering, grafting etc. of plants.
Role of nucleus in the heredity of organisms
- Nucleus helps cell meiosis in cell division. In the process of meiosis, sperm and ovum are formed from the generative mother cells. Sperm and egg play a major role in heredity through sexual intercourse.
- Nucleus contains chromosomes. Chromosomes contain DNA. DNA acts as the container and carrier of heredity. It carries hereditary characteristics. It transfers the characteristics of the parent to the offspring.