In every living cell, many biochemical reactions and processes occur. To control them, as well as regulate many vital factors, a special structure is needed. What is the core in biology? How does it effectively cope with the task?
What is the core in biology. Definition
The nucleus is the necessary structure of any cell in the body. What is a core? In biology, it is an essential component of every organism. The nucleus can be found both in unicellular protozoa and in highly organized representatives of the eukaryotic world. The main function of this structure is the storage and transfer of genetic information, which is also contained here.
After the sperm fertilizes the egg, two haploid nuclei merge. After the fusion of germ cells, a zygote is formed, the nucleus of which already carries a diploid set of chromosomes. This means that the karyotype (genetic information of the nucleus) already contains copies of the genes of both the mother and father.
The diploid nucleus is present in almost all eukaryotic cells. The haploid nucleus is possessed not only by gametes, but also by many representatives of simple organisms. This includes some unicellular parasites, algae, free-living forms of unicellular. It is worth noting that most of these representatives have a haploid nucleus only at a certain stage of the life cycle.
Core composition
What is the core feature? Biology carefully studies the composition of the nuclear apparatus, because it can give an 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 formed substances from the cell. The contents of the nucleus is called nucleoplasm.
Chromatin is the main substance of the nucleoplasm. The composition of chromatin 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 during division that double, after which each of their sets passes into daughter cells.
RNA in the nucleoplasm is most often found in two types: mRNA and rRNA. Matrix RNA is formed during transcription - reading information from DNA. The molecule of such ribonucleic acid later leaves the nucleus and subsequently serves as a matrix for the formation of new proteins.
Ribosomal RNA is formed in special structures called nucleoli. The nucleolus is built from the terminal sections of chromosomes formed by secondary constrictions. This structure can be seen in a light microscope in the form of a compacted spot on the nucleus. The ribosomal RNAs that are synthesized here also enter the cytoplasm and then form ribosomes together with proteins.
The composition of the nucleus has a direct effect on the function. Biology as a science studies the properties of chromatin to better understand the processes of transcription and cell division.
Kernel functions. Biology of processes in the core
The first and most important function of the kernel is the storage and transmission of hereditary information. The nucleus is a unique cell structure, because 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: the gametes are haploid, and somatic cells are diploid. Endosperm cells of angiosperms are triploid, and finally, many cultivars have a polyploid chromosome set.
The transmission of hereditary information to the cytoplasm from the nucleus occurs during the formation of mRNA. During the transcription, the necessary karyotype genes are read, and as a result, the molecules of messenger or messenger RNA are synthesized.
Also, heredity is manifested in cell division by mitosis, meiosis or amitosis. In each of the cases, the kernel performs its specific function. For example, in the prophase of mitosis, the membrane of the nucleus is destroyed and highly compacted chromosomes enter the cytoplasm. However, in meiosis, before collapse of the membrane, chromosome crossing over occurs in the nucleus. And in amitosis, the nucleus completely collapses and makes a small contribution to the fission process.
In addition, the nucleus is indirectly involved in the transport of substances from the cell due to the direct connection of the membrane with EPS. This is what the core is in biology.
Cores shape
The nucleus, its structure and functions may depend on the shape of the membrane. The nuclear apparatus can be round, elongated, in the form of blades, etc. Often, the shape of the nucleus is specific to individual tissues and cells. Unicellular organisms differ in the type of nutrition, life cycle, and at the same time, the forms of the membrane of the nuclei also differ.
The diversity in the shape and size of the nucleus can be traced on the example of white blood cells.
- The neutrophil nucleus may be segmented and not segmented. In the first case, they talk about a horseshoe-shaped nucleus, and this form is characteristic of young cells. A segmented core is the result of the formation of several partitions in the membrane, resulting in the formation of several parts interconnected.
- In eosinophils, the nucleus has a characteristic dumbbell shape. In this case, the nuclear apparatus consists of two segments connected by a partition.
- Almost the entire volume of lymphocytes is occupied by a huge nucleus. Only a small part of the cytoplasm remains on the periphery of the cell.
- In glandular cells of insects, 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 is only one core. Sometimes it is necessary to have two or more nuclear devices to carry out several functions simultaneously. Conversely, some cells can do without a nucleus at all. Here are some examples of unusual cells in which there are more than one nucleus or no nuclei at all.
1. Red blood cells and platelets. These blood cells transport hemoglobin and fibrinogen, respectively. So that one cell can accommodate the maximum amount of substance, it has lost its core. This feature is characteristic not for all representatives of the animal world: frogs have huge red blood cells with a pronounced nucleus in the blood. 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 will subsequently become part of the blood hemoglobin.
3. Myocytes of striated skeletal tissue. Muscle cells are multinucleated. This is due to the fact that ATP synthesis and decay, as well as protein assembly, are actively taking place in them.
Features of the nuclear apparatus in the simplest
For example, consider two types of protozoa: ciliates and amoeba.
1. Infusoria shoe. This representative of unicellular organisms has two nuclei: vegetative and generative. Since they differ both in function and in size, this feature is called nuclear dualism.
The vegetative nucleus is responsible for the daily life of the cell. It regulates the processes of its metabolism. The generative nucleus is involved in cell division and conjugation, the sexual process in which genetic information is exchanged with individuals of the same species.
2. Amoeba. Bright representatives are dysenteric and intestinal amoeba. The first refers to aggressive parasites of the person, and the second - the usual symbiont, which lives in the intestines and does no harm. Since dysenteric amoeba also parasitizes in the intestine, it is important to distinguish between these two species. To do this, use the peculiarity of the nuclear apparatus: a dysenteric amoeba can have up to 4 nuclei, and an intestinal amoeba from 0 to 8.
Diseases
Many genetic diseases are associated with abnormalities in the set of chromosomes. Here is a list of the most famous abnormalities in the genetic apparatus of the nucleus:
- Down syndrome;
- Patau ciddrome;
- Edwards syndrome ;
- Klinefelter syndrome;
- Shereshevsky-Turner syndrome.
The list goes on, and each of the diseases differs in the serial number of a pair of chromosomes. Also, similar diseases often affect the sex X and Y chromosomes.
Conclusion
The nucleus plays an important role in the life of the cell. It regulates biochemical processes, is a repository of hereditary information. The transport of substances from the cell, protein synthesis are also associated with the functioning of this central cell structure. This is what the core is in biology.