What is the core in biology? Structure and functions of the kernel

In each living cell, there are many biochemical reactions and processes. To control them, and to regulate many vital factors, a special structure is needed. What is the core in biology? Due to what it effectively copes with the task?

What is the core in biology. Definition

The nucleus is the necessary structure of any cell in the body. What is the core? In biology, this is the most important component of every organism. The nucleus can be found in unicellular protozoa as well as in highly organized representatives of the eukaryotic world. The main function of this structure is the storage and transfer of genetic information, which is contained here.

After the fertilization of the ovum with the spermatozoon, two haploid nuclei are fused. After the fusion of the sex cells, a zygote is formed, the nucleus of which already carries a diploid set of chromosomes. This means that the karyotype (the genetic information of the nucleus) already contains copies of the genes of both the mother and the father.

The diploid nucleus is present in virtually all eukaryotic cells. Haploid nucleus is possessed not only by gametes, but also by many representatives of the simplest organisms. This includes some unicellular parasites, algae, free-living forms of unicellular organisms. It should be noted that most of the listed representatives have a haploid core only at a certain stage of the life cycle.

Kernel composition

What is the characteristic of the nucleus? Biology carefully studies the composition of the nuclear apparatus, since it can give impetus to the development of genetics, selection and molecular biology.

The core is a two-membrane structure. Membranes are a continuation of the endoplasmic reticulum, which is necessary for the transport of the formed substances from the cell. The core content is called nucleoplasm.

Chromatin is the basic substance of nucleoplasm. The chromatin composition is diverse: here are primarily nucleic acids (DNA and RNA), as well as proteins and many metal ions. DNA in the nucleoplasm is arranged in the form of chromosomes. It is the chromosomes that divide in division, after which each of their sets passes into daughter cells.

RNA in the nucleoplasm most often occurs in two types: mRNA and rRNA. Matrix RNA is formed during the process of transcription - the reading of information from DNA. A molecule of such a ribonucleic acid later leaves the nucleus and further serves as a matrix for the formation of new proteins.

Ribosomal RNA is formed in special structures called nucleoli. The nucleolus is constructed from the terminal regions of the chromosomes formed by secondary constrictions. This structure can be seen in a light microscope in the form of a compact spot on the nucleus. Ribosomal RNAs, which are synthesized here, also enter the cytoplasm and then form ribosomes together with proteins.

The composition of the nucleus exerts a direct influence on the functions. Biology as a science studies the properties of chromatin for a better understanding of the processes of transcription and cell division.

Functions of the kernel. Biology of processes in the nucleus

The first and most important function of the kernel is the storage and transmission of hereditary information. The nucleus is a unique structure of the cell, since it contains most of the human genes. The karyotype can be haploid, diploid, triploid and so on. The ploidy of the poison depends on the function of the cell itself: gametes are haploid, and somatic cells are diploid. Endosperm cells of angiosperm plants are triploid, and, finally, many varieties of sowing cultures have a polyploid set of chromosomes.

The transfer of hereditary information to the cytoplasm from the nucleus occurs when mRNA is formed. During the transcription, the necessary karyotype genes are read, and eventually the molecules of the matrix or information RNA are synthesized.

Also, heredity manifests itself in cell division by mitosis, meiosis or amitosis. In each case, the kernel performs its specific function. For example, in the prophase of mitosis, the shell of the nucleus collapses and the highly compacted chromosomes enter the cytoplasm. However, in meiosis, chromosome crossing occurs before the destruction of the membrane in the nucleus. And in amitosis, the nucleus is completely destroyed and contributes a little to the process of division.

In addition, the nucleus indirectly participates in the transport of substances from the cell due to the direct connection of the membrane with EPS. That's what a nucleus is in biology.

Form of nuclei

The core, its structure and functions can depend on the shape of the membrane. The nuclear apparatus can be rounded, elongated, in the form of blades, etc. Often the shape of the nucleus is specific for individual tissues and cells. Unicellular organisms differ in the type of nutrition, life cycle, and at the same time, the shape of the membrane of the nuclei also varies.

Variety in the shape and size of the nucleus can be traced to the example of leukocytes.

• The nucleus of neutrophils can be segmented and not segmented. In the first case we speak of a horseshoe-shaped nucleus, and this form is characteristic of young cells. Segmented core is the result of the formation of several partitions in the membrane, resulting in the formation of several parts that are linked together.
• In eosinophils, the nucleus has a characteristic dumbbell shape. In this case, the nuclear apparatus consists of two segments connected by a septum.
• Almost the entire volume of lymphocytes is occupied by a huge nucleus. Only a small part of the cytoplasm remains around the periphery of the cell.
• In ferruginous insect cells, the nucleus may have a branched structure.

The number of nuclei in one cell can be different

Not always in the cell of the body there is only one nucleus. Sometimes the presence of two or more nuclear devices is necessary to perform several functions simultaneously. Conversely, some cells can do without a kernel at all. Here are some examples of unusual cells in which there are more than one nucleus or none at all.

1. Erythrocytes and platelets. These blood elements transport hemoglobin and fibrinogen, respectively. For one cell to hold the maximum amount of matter, it lost its nucleus. This feature is not typical for all the representatives of the animal world: frogs have huge red blood cells with a pronounced nucleus. This shows the primitiveness of this class in comparison with more developed taxa.

2. Hepatocytes of the liver. These cells contain two nuclei. One of them regulates the purification of blood from toxins, and the other is responsible for the formation of gem, which in the future will be part of the hemoglobin of the blood.

3. Myocytes of transverse striated skeletal tissue. Muscle cells are multinucleated. This is due to the fact that they actively undergo synthesis and decomposition of ATP, as well as the assembly of proteins.

Features of the nuclear apparatus in protozoa

For example, consider two types of protozoa: infusoria and amoeba.

1. Infusoria-shoe. This representative of unicellular organisms has two nuclei: vegetative and generative. Because they differ in both functions and sizes, this feature is called nuclear dualism.

The vegetative core is responsible for the daily life of the cell. It regulates the processes of its metabolism. The generative nucleus participates in cell division and in conjugation, the sexual process in which genetic information is exchanged with individuals of the same species.

2. Amoeba. Bright representatives - dysenteric and intestinal amoeba. The first refers to aggressive human parasites, and the second is an ordinary symbiont that lives in the intestine and does no harm. Because dysenteric amoeba parasitizes also in the intestine, it is important to distinguish these two species among themselves. To do this, use a feature of the nuclear apparatus: the dysenteric amoeba can have up to 4 cores, and in the intestinal amoeba, from 0 to 8.

Diseases

Many genetic diseases are associated with disorders in the recruitment of chromosomes. Here is a list of the most known deviations in the genetic apparatus of the nucleus:

• Down syndrome;
• Siddrum Patau;
• Edwards syndrome ;
• Klinefelter's syndrome;
• Shereshevsky-Turner syndrome.

The list goes on, and each of the diseases differs by the serial number of a pair of chromosomes. Also, these diseases often affect the sex X and Y chromosomes.

Conclusion

The nucleus plays an important role in the process of cell activity. It regulates biochemical processes, is the storehouse of hereditary information. Transport of substances from the cell, the synthesis of proteins are also associated with the functioning of this central cell structure. That's what a nucleus is in biology.