Almost all living organisms on Earthneed a breathing process. Oxygen is one of the most common oxidants in the respiratory chain of animals, plants, protists, many bacteria. However, not everyone knows how much our body differs in complexity of structure from small cells of microorganisms. The question arises: how do bacteria breathe? Is their way of receiving energy from ours different?
Not everyone knows that oxygen is not alwaysan obligatory component in the respiratory chain. It plays, first of all, the role of an electron acceptor, so this gas oxidizes well and interacts with hydrogen protons. ATP is the reason why all living organisms breathe. However, many types of bacteria do without oxygen, and still receive such a cherished source of energy, as adenosine triphosphate. How do bacteria of this type breathe?
The process of breathing in our body proceeds ontwo stages. The first of them - anaerobic - does not require the presence of oxygen in the cell, and for it only carbon sources and acceptors of hydrogen protons are needed. The second stage - aerobic - takes place exclusively in the presence of oxygen and is characterized by a large number of stage-by-stage reactions.
Bacteria that do not absorb oxygen and do notuse it for breathing, only the anaerobic stage proceeds. At its end, microorganisms also receive ATP, but its amount is very different from the one we get after passing through two stages of respiration. It turns out that not all bacteria breathe oxygen.
It is important for any organism to maintain its ownlife activity. Therefore, it was necessary in the process of evolution to find sources of energy that, when used, can provide enough resources for the flow of all necessary reactions in the cell. First there was fermentation in bacteria: the so-called stage of glycolysis or the anaerobic stage of prokaryotic breathing. And only later, in more sophisticated multicellular organisms, adaptations developed, thanks to which, with the participation of atmospheric oxygen, the respiratory efficiency increased markedly. So there was an aerobic stage of cellular respiration.
How do bacteria breathe? 6th grade of the school biology course shows that for any organism it is important to obtain a certain share of energy. In the process of evolution, it began to be stored in specially synthesized molecules, called adenosine triphosphate.
ATP is a macroergic substance,the basis of which is a pentose carbon ring, a nitrogenous base (adenosine). Phosphoric residues leave it, between which high-energy bonds are formed. When one of them is destroyed, an average of about 40 kJ is released, and one ATP molecule can store a maximum of three phosphorus residues. So, if ATP breaks down to ADP (adenoside diphosphate), then the cell gets 40 kJ of energy in the process of dephosphorylation. And, on the contrary, storage takes place by phosphorylation of ADP to ATP with energy expenditure.
Glycolysis gives the cell a bacterium of 2 moleculesadenosine triphosphate, when the aerobic stage of breathing can complete the cell immediately with 36 molecules of this substance. Therefore, the answer to the question "How do bacteria breathe?" Is as follows: the process of breathing for many prokaryotes is the formation of ATP without the presence and cost of oxygen.
With respect to oxygen, all prokaryotes are divided into several groups. Among them:
The first group consists only of those bacteria,who can not live in conditions of access to oxygen. O2 for them is toxic and leads to cell death. Examples of such bacteria are purely symbiotic prokaryotes that live inside another organism in the absence of oxygen.
The second group combines such types of prokaryotes,which actively multiply and grow in the absence of oxygen, however, its small percentage in the environment does not lead to lethal consequences. Such bacteria include saprophytes and some parasites.
How do bacteria of the third group breathe? These prokaryotes differ in that they can live only in conditions of good aerolization. If there is not enough oxygen in the air, such cells quickly die, because they need O2 for breathing.
Fermentation in bacteria is the same processglycolysis, which in different types of prokaryotes can give different reaction products. For example, lactic fermentation leads to the formation of a by-product of lactic acid, alcohol fermentation - ethanol and carbon dioxide, oil-sour-butane (butanoic acid), etc.
Oxygen breathing is a complete chain of processes,which begin with the stage of glycolysis with the formation of pyruvic acid, and end with the release of CO2, H2O and energy. The last reactions take place in the presence of oxygen.
At school, we were given only a simple knowledge of how,how the process of breathing prokaryotes occurs. There are no mitochondria in these microorganisms, however, there are mesosomes - protrusions of the cytoplasmic membrane inside the cell. But these structures play not the most key role in the respiration of bacteria.
Since fermentation is a kind of glycolysis,then it proceeds in the cytoplasm of the prokaryotes. There are also numerous enzymes necessary for carrying out the entire chain of reactions. In all bacteria, without exception, two molecules of pyruvic acid, as in man, are first formed. And only then they turn into other by-products, which depend on the type of fermentation.
The world of prokaryotes, despite the apparent simplicitycellular organization, is full of complex and sometimes unexplained moments. Now there is an answer to how the bacteria really breathe, because not all of them need oxygen. On the contrary, most have adapted to use another, less practical way of obtaining energy - fermentation.
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