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.