Prokaryotic cells: what are they and what are their characteristics?

A summary of what prokaryotic cells are and their biological characteristics.

In taxonomy and phylogeny, animals are a kingdom of living beings that brings together a large group of organisms. All the members of this taxon have a series of characteristics in common: they are eukaryotic (they have a delimited nucleus in the cell), heterotrophic, multicellular, with organization in the form of tissues and organs, ample capacity for movement and embryonic development with common patterns.

As you may already know, human beings belong to this group, since we are still bipedal vertebrate animals, despite the fact that we are moving further and further away from natural selection and the biological processes that characterize the rest of living beings. For our part, the human being is composed of 30 million million million cells, 84% of which are red Blood cells or red blood cells, responsible for transporting oxygen in the blood to all our organs.

With these lines we have described the multicellular eukaryotic living beings, that is, invertebrates, fish, birds, reptiles, amphibians and mammals. However, we cannot forget that there is a microscopic world that, although it is not visible to the naked eye, is one of the most important bases of all ecosystems on Earth. Today we tell you all about prokaryotic cells and the organisms that have them. and the organisms that have them. Do not miss 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 the nucleoid.The genetic material is found in the cytoplasm, grouped in an area called the nucleoid. Prokaryotic microorganisms are almost without exception unicellular, and include the taxonomic groups of bacteria and archaea.

Although there are a number of vital differences between the cells of animals, plants and fungi and those that make up the bodies of many microorganisms, every cell must have a number of basic "ingredients" to be considered as such. Among them, we find the following:

• Plasma membrane: an outer covering of lipid nature (bilayer) that delimits the entire cell, differentiating the extracellular from the intracellular medium.
• Cytosol: the liquid medium found inside the cells. It consists of a very fine colloidal dispersion with a granular appearance.
• DNA (nucleoid): the genetic material of the cell. Without it, cell replication and division are completely impossible.
• Ribosomes: make DNA transcription possible, through the formation of proteins essential for cell maintenance and metabolism.
• Compartments typical of prokaryotes, such as chlorosomes, carboxysomes, magnetosomes and others.

With the exception of the compartments typical of prokaryotes, all the items we have mentioned in this list are essential for a cell to be considered as such. Because of this very specific definition, viruses would be left out of the group of microorganisms and, therefore, could not be considered as living beings. beings.

The viral dilemma

Before continuing with the study of prokaryotes, it is very interesting to pose the following dilemma: are viruses alive? The answer, at least strictly speaking, is that they are not.

The basic unit of life is the cell.The virus must have all the components mentioned above. Although a virus has a sort of "membrane" that delimits it from the environment (protein capsid) and genetic information in the form of DNA or RNA, it has no cytosol, ribosomes or other organelles. Since it does not have ribosomes, it is not capable of synthesizing proteins on its own and therefore cannot reproduce autonomously: this is where viruses fail as living beings.

Because of this primordial mechanism, all viruses are parasites. They must enter a host cell, take advantage of its replication mechanism and multiply thanks to their complex machinery. Without the ribosomes and other organelles of their host, viruses could not persist at the evolutionary level.

Other characteristics of prokaryotic cells

As mentioned above, there are some organelles that are unique to these cell types. One example is phycobilisomes, water-soluble pigment complexes that serve primarily as light-receiving antennae in cyanobacteria and red algae. Also magnetosomes, intracellular magnetite crystals that allow bacteria to arrange themselves in the environment according to magnetic polarity. according to magnetic polarity.

More well known are flagella, fimbriae and pili, proteinaceous 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 organisms would not be able to interact with the environment.

Multicellular animals can "afford" to organize our tissues on the basis of their functionality, which is why we possess legs, sense organs and evolutionarily advanced structures that allow us to develop in a three-dimensional environment. Since microorganisms are unicellular, natural selection must "figure out" how to accumulate the maximum possible number of adaptations in an extremely limited environment, such as the envelope of a single cell.such as a cell envelope and its cytosol. The previously named organelles and structures exemplify this.

The importance of prokaryotes on Earth

It may seem that prokaryotes do not play an essential role in ecosystems because they are invisible to the human eye and, as such, should be relegated to a minor conservation role. Nothing could be further from the truth: we show you the importance of prokaryotic cells with a series of easy-to-understand facts.

It is estimated that on planet Earth there are about 550 billion tons (550 gigatons or Gt) of carbon, a chemical element that represents the amount of biomass (organic matter) available for the existence of living beings.The 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.

It would be logical to think that humans and other animals would come in second place, right? Well, no. It is shocking to learn that the second largest contributors are bacteria, which contribute 70 gigatons of carbon to the Earth (15% of the total). Sadly, animals barely contribute more than 2 Gt of organic matter to ecosystems.

The functionality of prokaryotic cells (bacteria and archaea) is not limited to the accumulation of biomass. Some are capable of transforming organic matter into inorganic matter (and vice versa), others carry out fermentation processes, are present in the carbon, phosphorus and nitrogen cycles and even synthesize oxygen, among many other things: in short, without bacteria, life would not be possible.

In short, without bacteria, life would not be possible, you don't need to go to the jungle to understand the essential nature of prokaryotic microorganisms: all you have to do is look in the mirror.. It is estimated that 39 trillion bacteria inhabit the interior and surface of the human being, many of them commensals, some potentially pathogenic and others symbionts, which allow us to conceive our species as it is today.

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 pathogens, secreting bactericides and occupying with high efficiency the ecological niche that are our internal cavities. Without bacteria, ecosystems would not exist, but neither would our body as we conceive it..

Summary

Prokaryotic cells are the "simplest" from an evolutionary point of view, but the organisms that present them (bacteria and archaea) are as important as the most complex living being you can think of, even more so. They are the first to colonize any environment, establish extremely complex biochemical relationships with the inorganic components of ecosystems and allow the entry, in the long term, of more advanced beings in the evolutionary scale.

If we want you to keep an idea of all that has been 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, i.e. the genetic information is "free" in the form of a nucleoid.The former do not have a nuclear envelope in their cytoplasm, i.e., the genetic information is "free" in the form of a nucleoid. Although they are considered simpler than the eukaryotic cell bodies that make up vertebrates and invertebrates, they are just as important as any other organic element present on Earth.

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