All the animals and plants we meet ineveryday life are multicellular organisms. However, there is also a microcosm, where creatures invisible to our eyes live. Sometimes they consist of a single cell. Therefore, they can be seen only under a microscope. What features can be isolated from unicellular organisms?
Cell structure: a scheme of a typical prokaryotic and eukaryotic cell
Живые организмы в природе могут быть unicellular or multicellular, eukaryotic or prokaryotic. Each individual group has its own characteristics in structure, physiology, biochemistry. What are the signs of a prokaryotic cell? First of all, it is the simplicity of the organization. This type of cell lacks a nucleus, and genetic information is enclosed in DNA. And in this form, it "floats" in the cytoplasm. Also characteristic feature is that such cells lack any organelles. Their functions replace the cytoplasmic membrane protrusions, which are called mesosomes. They are in most cases responsible for respiration or photosynthesis.
В прокариотических клетках поверхностный аппарат it is quite difficult, because it is represented by several layers. The first of these, the cytoplasmic membrane, plays a crucial role in the transport of substances between the cell and the environment. CPM is represented by the bilipid layer, in which various proteins are anchored. Next, the prokaryotic cell is covered with a shell, which has a protective and adaptive nature. The second layer prevents the penetration of toxic substances. It protects against the effects of damaging factors, although this envelope also has its limits.
The last layer of the surface apparatus may notalways attend. It is a slimy sheath. First, it helps the cell in the process of movement, reducing friction. Secondly, the mucous sheath contains products of metabolism and secretion of these cells. These substances can be used for defensive purposes or, on the contrary, for attacking their victims. All prokaryotic organisms are composed of a single cell. These include primarily bacteria.
Features of eukaryotes
Эукариотические клетки отличаются своей the complexity of the organization. They have a large number of formations and structures, and numerous biochemical processes require the presence of many specific enzymes and formations. What is the living cell of eukaryotes? Its structure includes the following elements:
- Core.
- Organelles and cytoplasm.
- Membrane and cytoskeleton.
Ядро – это центральная структура любой eukaryotic cell in which hereditary information is stored. It contains chromosomes and nucleoli. They are responsible for the transfer and implementation of genetic information. Among the organelles, cells secrete:
- Two-membrane structures (mitochondria and plastids).
- Single-membrane structures (lysosomes, Golgi apparatus, endoplasmic reticulum, vacuoles, peroxisomes, etc.).
- Non-membrane structures (ribosomes, cytoskeleton).
The eukaryotic membrane is similar in structurein prokaryotes. However, it is more complex organization. A eukaryotic cell is made up of parts called compartments. Such a system of organization greatly simplifies the course of all biochemical processes, since the cell is divided into different compartments.
Protists - unicellular eukaryotic organisms
Среди всего многообразия эукариотических The organisms to which we belong are also less visible to the human eye. They are called protists. They constitute a separate kingdom in systematics. All protists are made up of a single cell, therefore, the size does not exceed 250 microns. They are divided into several groups, among which are sarcodic, flagellates, ciliates.
Type Sarkodovye
These include amoebas, which consist of onecells These creatures inhabit the soil, fresh or salt water. Their body does not have a permanent form, which allows them to form so-called legs, with which these protists seize their food.
Type Flagellates
Жгутиконосцы получили свое название из-за наличия flagellum at the end of the body. It allows such cells to move quickly. This makes flagellates excellent hunters. Among them emit a large number of parasites of higher multicellular organisms. The body of such creatures has a permanent form due to the sweaty cell wall.
Type of ciliates
Infusoria consist of a single cell.Despite this, they are considered to be evolutionarily the most developed among the simplest. There was even a theory of the formation of multicellular animals, according to which they evolved from ciliates. These creatures have a dense cell wall. They have two nuclei in the cytoplasm: the generative, which controls reproduction, and the vegetative, which is responsible for vital processes. The entire body of the ciliates is covered with cilia. Metabolism products are removed through a special hole - poroshitsu.
Human cells: a variety of forms and structural features
Our body is a multicellulara formation in which cells are connected to each other. They transmit information using synthesized signaling substances. They form tissues, organs and systems that differ functionally and morphologically from each other.
What does a human cell consist of?If we consider the cells of any tissue of the body, they have all the signs of eukaryotes: the nucleus, organelles, the cytoskeleton, the complexity of the organization of metabolism. However, among them it is possible to find exceptions that give the uniqueness of a particular fabric.
For example, red blood cells do not have a nucleus.This gives them the ability to bind more oxygen or carbon dioxide. The ovum can reach 0.12-0.15 cm in diameter, which is a very large value even for a eukaryotic cell. Human neurons also have their own characteristics. They form numerous outgrowths, among which are short dendrites and long axons.
