The cells of all living organisms have a similar structure. All of them consist of a plasma membrane, a membrane around it (glycocalyx in animals or the cell wall: in fungi - from chitin, in plants - from cellulose), cytoplasm (there are organoids in it, each of which performs its functions, a cell center, for example takes part in fission) and the nucleus that protects DNA (except prokaryotes).
Cell organelles
These include ribosomes, lysosomes, mitochondria, the Golgi complex, endoplasmic reticulum and cell center. Plant cells also contain specific organoids inherent only to them - vacuoles. They accumulate unnecessary substances, plastids (chromoplasts, leukoplasts, chloroplasts, in the latter there is a process of photosynthesis). The functions of the cell center, mitochondria, ribosomes and other structures are very important. Mitochondria play the role of peculiar stations for energy production, the process of intracellular respiration takes place in them. Ribosomes are responsible for the production of proteins, synthesizing them from individual amino acids in the presence of mRNA, on which information about the substances necessary for the cell is recorded. The functions of lysosomes are to break down chemical compounds using enzymes that are contained within the organoid. The Golgi complex accumulates and stores certain substances. The endoplasmic reticulum also takes part in the metabolism.
Cell center - structure and functions
This organoid is also called a centrosome. It is difficult to overestimate the functions of the cell center - without this organoid, cell division would not be possible . It consists of two parts. In this, the cell center is similar to the ribosome, in the structure of which two halves are also present. Parts of the centrosome are called centrioles; each of them looks like a hollow cylinder formed of microtubules. They are perpendicular to each other. The functions of the cell center are the formation of centrioles of the spindle of division during meiosis or mitosis.
How is the cell divided?
There are two main ways - meiosis and mitosis. The functions of the cell center are manifested in both processes. In both the first and second cases, division occurs in several stages. These stages are distinguished: prophase, metaphase, anaphase, telophase.
Meiosis, as a rule, implies two consecutive cell divisions, the time between them is called interphase. As a result of this process, several with a
haploid (single) are formed from a cell with a diploid set of chromosomes (double
). In the process of mitosis, the number of chromosomes does not decrease - daughter cells also have a diploid set. There is also such a division method as amitosis. In this case, the nucleus, and then the entire cytoplasm, are simply divided in two. This species is far from as common as the first two; it is found mainly among protozoa. The cell center is not involved in this process.
Cell center involvement in division
Prophase implies preparation for the process of mitosis or meiosis, during which nuclear membranes are destroyed. During metaphase, the cell center is disconnected into two separate centrioles. They, in turn, diverge to the opposite poles of the cell. At the same stage, chromosomes line up along the equator. Then they are attached to the centrioles by the fission spindle threads so that the different chromatids of each chromosome are attached to the opposite centrioles. Throughout the metaphase, each of the chromosomes is split into separate chromatids, which centrioles for the strands attract to opposite poles.
During the telophase, the formation of nuclear membranes takes place, the cytoplasm is separated and daughter cells are finally formed.