Prokaryotic cells: what are they and what are their characteristics
In taxonomy and phylogeny, animals are a kingdom of living beings that brings together a wide group of organisms. All the members of this taxon have a series of characteristics in common: they are eukaryotes (they have a delimited nucleus in the cell), heterotrophic, multicellular, with organization in the form of tissues and organs, extensive capacity for movement, and embryonic development with patterns common.
As you already know, human beings are within this group, since we do not stop being bipedal vertebrate animals, despite moving further and further away from natural selection and the biological processes that characterize other beings alive. For our part, the human being is made up of 30 million million cells, 84% of which are They are the red blood cells or red blood cells, responsible for transporting oxygen in the blood to all our organs.
With these lines we have described multicellular eukaryotic living beings, that is, invertebrates, fish, birds, reptiles, amphibians and mammals. In any case, we cannot forget that there is a microscopic world that, although it cannot be observed with the naked eye, represents one of the most important bases of all the Earth's ecosystems. Today
we tell you everything about prokaryotic cells and the organisms that present them. Do not miss it.- Related article: "Animal cell: types, parts and functions that characterize it"
What are prokaryotic cells?
The prokaryotic cell is defined as the cell body of a unicellular organism without a nucleus (prokaryote), whose genetic material is found in the cytoplasm., grouped in an area called nucleoid. Prokaryotic microorganisms are almost without exception unicellular, and comprise the taxonomic groups of bacteria and archaea.
Despite the fact that there are a number of vital differences between the cells of animals, plants and fungi that make up the In the body of many microorganisms, every cell must present a series of basic "ingredients" to be considered as such. Among them, we find the following:
- Plasma membrane: an external cover of a lipid nature (bilayer) that delimits the entire cell, differentiating the extracellular from the intracellular environment.
- Cytosol: the liquid medium found inside cells. It consists of a very fine colloidal dispersion with a granular appearance.
- DNA (nucleoid): the genetic material of the cell. Without it, cell division and replication are completely impossible.
- Ribosomes: make possible the transcription of DNA, through the formation of essential proteins for cell maintenance and metabolism.
- Compartments typical of prokaryotes, such as chlorosomes, carboxysomes, magnetosomes, and others.
Except for the compartments characteristic of prokaryotes, all the points that we have mentioned in this list are essential for a cell to be considered as such. Due to this very specific definition, viruses would be left out of the group of microorganisms and, therefore, could not be considered as living beings to use.
The viral dilemma
Before continuing with the study of prokaryotes, it is very interesting to ask the following dilemma: are the viruses alive? The answer, at least strictly speaking, is no.
The basic unit of life is the cell., and this has to present all the aforementioned components. Although a virus has a kind of "membrane" that delimits it from the environment (protein capsid) and genetic information in the form of DNA or RNA, it does not have a cytosol, ribosomes or other organelles. Not having ribosomes, it is not capable of synthesizing proteins on its own and, therefore, it cannot reproduce autonomously: this is where viruses fail as living beings.
Due to this very primitive mechanism, all viruses are parasites. These must enter a host cell, take advantage of its replication mechanism, and multiply thanks to its complex machinery. Without their host's ribosomes and other organelles, viruses could not persist at an evolutionary level.
- You may be interested in: "Endosymbiotic Theory: The Origin of Cell Types"
Other characteristics of prokaryotic cells
As we have said before, there are some organelles that are exclusive to these cell types. An example of this are phycobilisomes, water-soluble pigment complexes that serve mainly as light-receiving antennae in cyanobacteria and red algae. Also Magnetosomes, intracellular magnetite crystals that allow bacteria to organize themselves in the environment, stand out for their interest. according to magnetic polarity.
Better known are the flagella, fimbriae and pili, protein appendages of variable hardness, thickness and length that allow microorganisms to move through the environment and interact with each other. Without these structures, many bacteria, protozoa, and other microscopic beings could not interact with their environment.
Multicellular animals can "allow" ourselves to organize our tissues based on their functionality, and for this reason we have legs, sense organs and evolutionarily advanced structures that allow us to develop in the environment three dimensional. Since microorganisms are unicellular, natural selection must "manage" to accumulate the maximum possible number of adaptations in an extremely limited environment., as is the covering of a cell and its cytosol. The previously named organelles and structures exemplify it.
The importance of prokaryotes on Earth
It may seem that prokaryotes do not play an essential role in ecosystems, since they are invisible to the human eye and, as such, should be relegated to minor conservation work. Nothing could be further from the truth: we show you the importance of prokaryotic cells with a series of data that is very easy to understand.
It is estimated that on planet Earth there are about 550,000 million tons (550 gigatonnes or Gt) of carbon, chemical element that represents the amount of biomass (organic matter) available for the existence of living beings. As you can imagine, most of this organic matter is stored in plants, which contribute 450 Gt of carbon, or 80% of the total.
The consequent thing would be to think that the human being and the rest of the animals would appear in second place, right? Well no. It is shocking to learn that the second largest contributors are bacteria, since they provide the Earth with 70 gigatonnes of carbon (15% of the total). Animals, sadly, barely contribute more than 2 Gt of organic matter to ecosystems.
The functionality of prokaryotic cells (bacteria and archaea) is not limited solely to the accumulation of biomass. Some are capable of transforming organic matter into inorganic (and vice versa), others carry out fermentation processes, are present in cycles of carbon, phosphorus, nitrogen and even synthesize oxygen, among many other things: in short, without bacteria, life would not be possible.
Anyway, nor is it necessary to go to the jungle to understand the essentiality of prokaryotic microorganisms: just look in the mirror. It is estimated that 39 billion bacteria live inside and on the surface of human beings, many of them commensals, some potentially pathogenic and others symbionts, which allow us to conceive our species as what it is today. day.
The highest concentration of bacteria in humans is found in the gastrointestinal tract, where they perform a number of invaluable functions. Among them, we can highlight that they "guide" our immune system at birth, allow us to metabolize substances of vegetable origin that we could not digest by ourselves and protect us from pathogenic agents, secreting bactericides and occupying with high efficiency the ecological niche that are our cavities internal. Without bacteria, ecosystems would not exist, but neither would our body as we conceive it..
Summary
Prokaryotic cells are the most "simple" from an evolutionary point of view, but the organisms that present (bacteria and archaea) are as important as the most complex living being you can think of, even further. They are the first to colonize any environment, they establish extremely complex biochemical relationships with inorganic components of ecosystems and allow the entry, in the long term, of beings more advanced in the scale evolutionary.
If we want you to keep an idea of everything exposed so far, it is the following: Prokaryotic cells differ from eukaryotic cells mainly in that the former do not have a nuclear envelope in their cytoplasm., that is, the genetic information is "free" in the form of a nucleoid. Although they are considered simpler than the eukaryotic cell bodies that make us up vertebrates and invertebrates, are just as important as any other organic element present in the Land.
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