What is a eukaryote? The answer to this question lies in the structural features of cells of various types. We will consider the nuances of their organization in our article.
Features of the structure of cells
The cells of living organisms are classified according to different characteristics. One of them is the organization of hereditary material contained in DNA molecules. Eukaryotes are organisms in the cells of which there is a shaped nucleus. This is a two-membered organelle containing genetic material. In prokaryotes, this structure is absent. Such organisms include all types of bacteria and archaea.
The structure of prokaryotic cells
The absence of a nucleus does not mean that prokaryotic organisms do not have hereditary material. It is also encoded in a nucleotide sequence. However, the genetic information is not located in the formed nucleus, but is represented by a single circular DNA molecule. It is called a plasmid. Such a molecule attaches to the inner surface of the plasma membrane. Cells of this type are also devoid of a number of specific organelles. Prokaryotic organisms are characterized by primitiveness, small size and low level of organization.
What is a eukaryote?
This large group of organisms includes all representatives of plants, animals, and fungi. Viruses are non-cellular life forms, therefore, are not considered in this classification.
The surface apparatus of prokaryotic cells is represented by a plasma membrane, and the inner contents by the cytoplasm. This is an internal semi-fluid medium that performs a support function, combines all structures into a single whole. Prokaryotic cells are also characterized by the presence of a certain number of organoids. This is the Golgi complex, endoplasmic reticulum, plastids, lysosomes. Some believe that eukaryotes are organisms in the cells of which there are no mitochondria. But this is not at all true. These organelles in eukaryotic cells serve as the site for the formation of ATP energy carrier molecules in the cell.
Eukaryotes: Examples of Organisms
Three kingdoms of wildlife are eukaryotes . However, despite the common features, their cells have significant differences. For example, plant species are characterized by the content of specialized chloroplast organelles. It is in them that the complex photochemical process of the conversion of inorganic substances into glucose and oxygen takes place. Animal cells do not have such structures. They can only absorb ready-made nutrients. These structures differ in the structure of the surface apparatus. In animal cells, glycocalyx is located above the plasma membrane. It is a viscous surface layer consisting of proteins, lipids and carbohydrates. For plants, the cell wall is characteristic . It is located above the plasma membrane. The cell wall is formed by complex carbohydrates, cellulose and pectin, which give it strength and rigidity.
What is a eukaryote that is represented by a group of fungi? The cells of these amazing organisms combine the structural features of both plants and animals. The composition of their cell wall includes carbohydrates cellulose and chitin. However, their cytoplasm does not contain chloroplasts, therefore, like animal cells, they are only capable of heterotrophic nutrition.
Progressive structural features of eukaryotes
Why are all eukaryotes are organisms that have reached a high level of development and spread around the planet? First of all, due to the high level of specialization of their organelles. The ring DNA molecule, which is contained in bacterial cells, provides the easiest way to multiply them - cell division in two. As a result of this process, exact genetic copies of daughter cells are formed. Reproduction of this type, of course, ensures the continuity of generations and provides a fairly quick reproduction of such cells. However, the appearance of new signs in the course of dividing in two is out of the question. And this means that these organisms will not be able to adapt to changing conditions. Eukaryotic cells are characterized by a sexual process. In its course there is an exchange of genetic information and its recombination. As a result, individuals with new, often useful traits that are fixed in their genotype and can be transmitted from generation to generation are born. This is a manifestation of hereditary variability, which is the basis of evolution.
So, in our article we examined what eukaryotes are. This concept means an organism whose cells contain a nucleus. This group of organisms includes all representatives of the plant and animal world, as well as fungi. The nucleus is a permanent cell structure that provides storage and transmission of hereditary information of organisms encoded in the nucleotide sequence of DNA molecules.