Human cell nucleus: structure, function and origin

The nucleus of the cell is the obligatory structure of each eukaryotic organism. This organelle performs a variety of functions, but its main purpose is the storage and transfer of hereditary genetic material.

Almost every cell of the human body has a nucleus. The only exception is platelets and red blood cells. Most cells are single-core, but, for example, muscle fibers and neurons can have several of these organelles. The nucleus in a cage can have different sizes - the largest nuclear structures in a female egg.

Cell nucleus: structure

The nucleus has a rather complex structure and consists of their nuclear envelope, chromatin, nucleolus and nucleoplasm. Let's look at each part of it in more detail.

• A karyoteka, or nuclear envelope, is a structure that separates the inner core environment from the cytoplasm. This shell consists of the outer and inner membranes, between which there is a so-called perinuclear space. Interestingly, the outer membrane of the membrane passes directly to the membrane of the granular endoplasmic reticulum, therefore the cavities of the EPS and core tanks are interconnected. And the shell has nuclear pores, closed diaphragm. They are designed to penetrate large molecules, as well as for the exchange of substances between the karyoplasm and the cytoplasm.
• Karyoplasm is a homogeneous substance that fills the inner cavity of the nucleus. It contains the nucleolus, as well as chromatin.
• Chromatin is the genetic material of the cell. Its structural unit is the nucleosome, which is a DNA strand wound on a specific protein - histone. Two cells of the genetic material are distinguished in the cell. Heterochromatin is a small, dense osmophilic granule. Euchromatin, or loosened chromatin - these are areas in which synthetic processes are active. During cell division, chromatin condenses, forming chromosomes.
• The nucleolus is a small, oval structure that consists of strands of RNA and protein molecules. It is here that the formation of subunits of ribosomes occurs. In the nucleus there may be one or more nucleoli, but they can be noticed only in nondividing cells.

Kernel Core: Functions

The functions of the cell nucleus can be determined by studying its structure. First, the nucleus is responsible for the transmission of the hereditary set of information during cell division, with both mitosis and meiosis. During mitosis, daughter cells receive a genome that is identical with the parent cell. When meiosis (the formation of human germ cells ), each cell receives only half of the chromosomal set - a complete set of chromosomes is formed only after merging with the sex cell of another organism.

In addition, the nucleus of the cell is responsible for one of the most important stages of metabolism - protein synthesis. The fact is that it is in the nucleus that information, or matrix RNA, is formed. Then it enters the endoplasmic reticulum, joins the ribosome and serves as a model for the formation of the amino acid sequence of the peptide molecule.

And, as already mentioned, the synthesis of subunits of the ribosome takes place in the nucleus.

Cell nucleus: origin

To date, there are several completely different hypotheses, with the help of which scientists are trying to explain how the nucleus was formed in the cell. But, unfortunately, none of these statements have yet been factually confirmed.

There is a theory that the nucleus as a cellular structure was formed as a result of the symbiosis of the bacterial cell and the archaea. Other scientists believe that the nucleus is the result of infection of the cell with a specific virus.

The most complete explanation is contained in the so-called ezemembrane hypothesis. According to her, in the process of evolution, another outer cell membrane appeared in the cell. At the same time, the old, internal membrane turned into a shell of the nucleus - over time a complex pore system arose in it, and then chromatin molecules began to concentrate in its cavity.