All living organisms are subdivided intoand cellular. Viruses and phages belong to the docellular. The second group, cellular, is divided into prokaryotes and eukaryotes, which are pre-nuclear and nuclear organisms.
Prokaryotes
The first cellular, prokaryotes, originated on Earthmore than 3 billion years ago. This was the greatest leap in the development of life. Prokaryotes are bacteria. Their structure is relatively simple. Heredity information, DNA, is in their primitive, containing little protein ring-shaped chromosome. It is located in a special area of the cytoplasm, a nucleoid that is not separated from the rest of the cell by a membrane. The main difference between prokaryotes and eukaryotes from each other is that in the cells of the first type the present nucleus is absent.
The cytoplasm of pre-stem cells has muchfewer cellular structures. Of these, ribosomes are known, eukaryoid cells smaller than ribosomes. The role of mitochondria in prokaryotes belongs to simple membrane structures. There is also no chloroplast in them. Prokaryotes have a plasma membrane, above which there is a cell membrane. They differ from eukaryotes in considerably smaller sizes. In some cases, the prokaryotes may be so-called plasmids - small, in the form of a ring, DNA molecules.
Eukaryotes
All nuclear cells differ in general planstructure and common origin. They originated from pre-nucleated cells 1.2 billion years ago. Their structure is much more complicated. Both prokaryotes and eukaryotes have a cellular membrane. But otherwise their structural and biochemical features are very different. The most important difference is that in nuclear cells there is a true nucleus in which their genetic information is stored.
The nucleus is delineated from the cytoplasm of a speciala membrane consisting of the outer and inner layers. It is similar to a plasma membrane, but contains pores. Thanks to them, an exchange is made between the cytoplasm and the nucleus. The cell's genome consists of a whole set of chromosomes, these prokaryotes and eukaryotes also differ from each other. DNA in the chromosomes of eukaryotes is associated with histone proteins.
In the nucleus of cells are nucleoli, in whichribosomes are formed. An unstructured mass, a karyoplasm, surrounds the chromosomes and nucleoli. Each species of animals and plants has its own, strictly defined set of chromosomes. When dividing cells, they are doubled and then distributed to daughter cells
If we consider prokaryotes and eukaryotes, the differences in them are also visible in the cytoplasm of cells.
For plant cells, the presence of a largecentral vacuoles and plastids. This vacuole can move the nucleus to the periphery of the cell. Nutrient reserve carbohydrate plant cell - starch. Outside, the plant cells are covered with a cell wall consisting of cellulose. In the cell center there is no centriole, which can be seen only in algae.
Animal cells do not have a central vacuole, plastids and a dense cell membrane. In the center of the cell there is a centriole. Reserve carbohydrate in animal cells - glycogen.
Cells of fungi centriole is not always. The cell wall consists of chitin, there is no plastids in the cytoplasm, but there is a central vacuole in the center of the cell. The reserve of carbohydrates is also glycogen.
In the cytoplasm of eukaryotes there are mitochondria,Golgi apparatus, lysosomes, endoplasmic reticulum, organoids of movement. Ribosomes in them are much larger than ribosomes of prokaryotes. The cytoplasm of the cell is divided into separate compartments, compartments, using special membranes consisting of lipids. Each of them has its own biochemical processes. It almost does not occur in prokaryotes.
In general, prokaryotes and eukaryotes express the laws of evolution, which is characterized by the movement from simpler forms to more complex ones.
However, pre-adherent cells are characterized by a largeplasticity and the variety of metabolic processes. Many bacteria can receive energy due to light or chemical reactions, exist in an environment devoid of oxygen (anaerobic bacteria). Thanks to this they fit into the picture of the modern world.
