What is the eukaryotic cell?
It is known as eukaryotic cell those in whose cytoplasm can be found a cell nucleus that contains the genetic material (DNA), unlike prokaryotic cells, whose genetic material is dispersed in the cytoplasm.
The appearance of this type of cells is considered an important evolutionary step since it laid the foundations for the future complexity and variety of pluricellular life, thus giving rise to the higher kingdoms ( animalia , plantae , fungi and protista ).
Living beings formed by eukaryotic cells are called eukaryotes.
Characteristics of the eukaryotic cell
Meaning of the term
The term eukaryotic comes from a similar Greek word: eukaryota , union of eu- (“true”) and karyon (“nut, nucleus”). Hence, the term would come to designate cells with a true nucleus, that is, with a core distinguishable from the rest of the cellular content.
The emergence of eukaryotic cells occurred at some point in the evolutionary cellular history, when there were only prokaryotic unicellular organisms, much simpler and smaller.
It is not known for sure how this leap occurred or what motivated this leap towards the cellular structural complexity without which life had been reduced to unicellular colonies.
There are several theories. The most accepted proposes the origin of these cells in the symbiogenesis between two prokaryotes: a bacterium and an archaea.
Both would have cohabited so closely that they ended up composing the same organism, with a higher level of complexity.
The eukaryotic organisms, whose cells have a defined cell nucleus – container of the genetic material of the whole living being – integrate all the kingdoms of multicellular and superior unicellular beings: the kingdoms of animals , plants , fungi and protists .
This shows the gigantic biodiversity that the development of the cell nucleus allowed.
The eukaryotic cell is constituted of the following parts:
- Cell or plasma membrane . A kind of “curtain” that surrounds the cell and delimits it, allowing both the access of desired substances to its interior and the expulsion of unwanted ones.
- Cell wall . Characteristic of plant cells and fungi, only, it is a wall of cellulose (plants) or chitin (fungi) that gives them resistance and a certain rigidity.
- Core . In it are contained the chromosomes, carriers of the genes, which are the minimum units of the genetic information of the living being (DNA). It is covered by a nuclear membrane .
- Cytoplasm . That of eukaryotic cells is composed mostly of water and several compartments separated by internal membranes, in which the organelles (the “organs” of the cell) are found. The latter are:
- Lysosomes . They contain digestive material necessary for the assimilation of the substances that enter the cell.
- Mitochondria . They are responsible for the metabolic process, that is, the production of energy from respiration or photosynthesis.
- Chloroplasts . They carry the chlorophyll, appear only in plant cells and have a green pigment that gives the plants their characteristic color.
Differences between eukaryotic and prokaryotic cell
We can summarize the main differences between these two types of cells in the following points:
- Presence of nucleus . The essential difference, because in the prokaryotes the genetic material is dispersed in the cytoplasm, instead of being contained in a nucleus.
- Type DNA . The DNA of prokaryotes is circular in shape; that of eukaryotes in a linear way.
- Typical cell size . Eukaryotes have a larger size (10-100 ?m) than prokaryotes (0.2-2.0 ?m).
- Reproduction . Cellular prokaryotes reproduce asexually, while eukaryotes exhibit sexual and asexual reproduction.
- Presence of cellular organelles . Exclusive to eukaryotes: mitochondria, lysosomes, chloroplasts, etc.
There are many types of eukaryotic cells but three are fundamentally different: animals, plants and fungi, each with substantial minimal differences:
- Vegetables . They present a cellular wall of cellulose and proteins, as well as chloroplasts for chlorophyll destined for photosynthesis. They have a large central vacuole, which gives the cell its shape.
- Fungi . They have a chitin cell wall, despite a lower cellular definition.
- Animals . They lack plastids and cell walls, centrioles and vacuoles of smaller size but greater abundance.
Eukaryotic cells have two fundamental functions: self-preservation and self-reproduction.
This means that their behaviors are governed by the most elementary principles of life, which are to obtain the necessary food to produce energy and, eventually, to allow the perpetuation of life through the creation of new individuals of the species.
Eukaryotic cells contain an organelle called mitochondria, which is essential for aerobic (air) metabolism.
Most of them obtain the necessary energy for their functioning of cellular respiration, oxidizing essential carbohydrates, or else of photosynthesis, in the case of plants, taking advantage of sunlight and water to produce energy.
The eukaryotic cells are ancient, dating from 1400 to 1600 million years, according to the existing fossil record; However, the prokaryotes were first and preceded by several million years, dating from 3450 to 3700 million years according to the fossil record.
In the classification of life there are not only the kingdoms (animal, plant, fungi, protists, bacteria and archaea) but two different domains in which it is grouped and that are just eukaryotes and prokaryotes.
In the first rank the first four groups enter and in the second the last two. This is how biology understands today the different ways of life cone