Biological oxidation.

energy can not exist without a living creature.For every chemical reaction, any process required her presence.Any person is easy to understand and feel.If the whole day to eat food, then by the evening, and perhaps before, the symptoms will begin increased fatigue, weakness, strength drops significantly.

What a way different organisms have adapted to the production of energy?Where does it come from and what processes occur at the same time inside the cage?Try to understand this article.

Energy production organisms

Whichever way no energy being consumed, the basis always lie OVR (redox reactions).Examples include different.The equation of photosynthesis, which carry green plants and some bacteria - is also OVR.Naturally, the process will differ depending on whether the living being is meant.

So, all the animals - is heterotrophic.That is, those organisms that are unable to form in a ready-organic compounds for further cleavage and release of chemical energy.

Plants, on the other hand, are the

most powerful producer of organic matter on our planet.They carried out a complicated and important process called photosynthesis, which is the formation of glucose from water, carbon dioxide under the influence of special substances - chlorophyll.A by-product is oxygen, which is the source of life for all aerobic living beings.

Redox reactions, examples of which illustrate this process:

  • 6CO2 + 6H2O = chlorophyll = C6H10O6 + 6O2;


  • carbon dioxide + hydrogen under the influence of oxide pigment chlorophyll (enzyme reaction) = monosaccharide + free molecular oxygen.

Also, there are also representatives of the biomass of the planet, which are able to use the energy of chemical bonds of inorganic compounds.They are called chemotroph.These include many types of bacteria.For example, microorganisms are hydrogen, oxidizing a substrate molecule in the soil.The process works as follows: 2H2 + 02 = 2H20.

history of the development of knowledge about the biological oxidation

process that underlies the energy, it is known today.This biological oxidation.Biochemistry as examined in detail the subtleties of all the stages and mechanisms of action that almost no mysteries.However, it was not always.

first mention of that in living beings there are complex transformations that are of the nature of chemical reactions, there were roughly in the XVIII century.That's when Antoine Lavoisier, the famous French chemist, turned his attention to how similar biological oxidation and combustion.He followed a rough path absorbed by breathing oxygen and concluded that inside the body there are processes of oxidation, but more slowly than the outside of the combustion of various substances.That is, the oxidizer - oxygen molecules - react with organic compounds, and particularly, with hydrogen and carbon from them, and complete conversion, accompanied by decomposition of the compounds.

However, although this assumption is essentially quite real, remained obscure many things.For example:

  • times similar processes, the conditions of flow should be identical, but the oxidation proceeds at a low body temperature;
  • action is not accompanied by the release of enormous amounts of heat and there is no formation of the flame;
  • survivors there are at least 75-80% of the water, but it does not prevent "burning" nutrients in them.

To answer all these questions and to understand what actually is the biological oxidation, it took more than a year.

There are different theories that implied the importance of the process of oxygen and hydrogen.The most common and most successful were:

  • theory Bach called peroxide;
  • Palladin theory, based on such a concept as "chromogens".

Later there were many scientists in Russia and other countries, which gradually make additions and changes to the question of what is the biological oxidation.Biochemistry of today, because of their work, can tell you about each of the reaction process.Among the most famous names in the field include the following:

  • Mitchell;
  • S. Severin;
  • Warburg;
  • VA Belitser;
  • Lehninger;
  • VP Skulachev;
  • Krebs;
  • Green;
  • Engelhardt;
  • Kaylin and others.

Types of biological oxidation

There are two main types of the process, that occur in different conditions.Thus, the most common in many species of micro-organisms and fungi way to convert received food - the anaerobic.This biological oxidation, which is carried out without oxygen and without his involvement in any form.These conditions are in places where there is no air access: underground, in rotting substrates, silts, clays, swamps and even in space.

This type of oxidation has another name - glycolysis.He is one of the stages more difficult and time consuming, but energy-rich process - the conversion or aerobic tissue respiration.This is the second type of the process.It occurs in all living things-aerobic heterotrophs, which use oxygen for respiration.

Thus, the following types of biological oxidation.

  1. glycolytic anaerobic way.It does not require the presence of oxygen and ends with different forms of fermentation.
  2. tissue respiration (oxidative phosphorylation) or aerobic species.It requires mandatory presence of molecular oxygen.


proceed to consider themselves directly to the features that contains biological oxidation.We define the basic compounds and their abbreviations, which will continue to be used.

  1. acetyl coenzyme A (acetyl-CoA) - condensation of oxalic acid and acetic acid, coenzyme, which is formed in the first step of the tricarboxylic acid cycle.
  2. Krebs cycle (citric acid cycle, citric acid) - a series of complex sequential redox transformations, accompanied by the release of energy, hydrogen reduction, education is important low molecular weight products.He is the main link catalysis and anabolism.
  3. over and over * H - dehydrogenase enzyme, stands for nicotinamide.The second formula - a molecule with an attached hydrogen.NADP - nikotinamidadenindinukletid phosphate.
  4. FAD and FAD * H - flavin adenine dinucleotide - coenzyme dehydrogenase.
  5. ATP - adenosine triphosphate.
  6. STC - pyruvic acid or pyruvate.
  7. succinate or succinic acid, H3PO4 - phosphoric acid.
  8. GTP - guanosine triphosphate, a class of purine nucleotides.
  9. ETC - electron transport chain.
  10. Enzymes process: peroxidase, oxygenase, cytochrome oxidase, flavin dehydrogenase coenzymes and various other compounds.

All of these compounds are directly involved in the oxidation process that occurs in the tissues (cells) of living organisms.

stages of biological oxidation: table

Stage Processes and value
Glycolysis essence of the process lies in the anoxic decomposition of monosaccharides, which precedes the process of cellular respiration and is accompanied by the release of energy, equal to two molecules of ATP.Pyruvate is also produced.This is the initial step for any living organism heterotrophic.The value in the formation of PVC, which is supplied to the mitochondrial cristae and a substrate for tissue oxygen by oxidation.In anaerobic glycolysis occur after the fermentation of various types.
oxidation of pyruvate This process is to convert STC formed during glycolysis, to acetyl-CoA.It is carried out by a specialized enzyme pyruvate dehydrogenase complex.Result - cetyl-CoA molecules, which enter into the Krebs cycle.The same process is carried out the restoration of NAD to NADH.Place localization - crista mitochondria.
Decay beta fatty acids This process is carried out in parallel with the previous Christie mitochondria.Its essence is to recycle all of the fatty acids to acetyl-CoA, and put it in the citric acid cycle.It also recovers NADH.
Krebs cycle

begins with the conversion of acetyl-CoA in the citric acid, which undergoes further transformations.One of the most important steps that include biological oxidation.This acid is treated:

  • dehydrogenation;
  • decarboxylation;
  • regeneration.

Each process is performed several times.Result: GTP, carbon dioxide, reduced form NADH and FADN2.This biological oxidation enzymes are freely located in the mitochondrial matrix particles.

Oxidative phosphorylation

This is the last step of converting compounds in eukaryotic organisms.This converts ADP to ATP.The energy required for this is taken by the oxidation of the molecules of NADH and FADN2 that formed in the previous stages.By successive transitions of ETC and reduced potential occurs conclusion energy-energy bonds of ATP.

It all processes that accompany the biological oxidation involving oxygen.Naturally, they are not fully described, but only in nature, for a detailed description need a whole chapter of the book.All the biochemical processes of living organisms is extremely multi-faceted and complex.

Redox reactions of

Redox reactions, examples of which are illustrated by the above-described oxidation of the substrate as follows.

  1. Glycolysis: monosaccharide (glucose) + + 2ADF 2NAD = 2PVK 2ATF + + 4H + + 2H2O NADH.
  2. oxidation of pyruvate: STC = enzyme + carbon dioxide + acetaldehyde.Then the next step: acetaldehyde + coenzyme A = acetyl-CoA.
  3. set of successive transformations of citric acid in the Krebs cycle.

These redox reactions, examples of which are listed above, reflect the essence of the processes taking place only in general terms.It is known that the compounds in question belong to the high-molecular, or having a large carbon skeleton, so to portray all the complete formula is just not possible.

energy yield of tissue respiration

In the above description it is evident that to calculate the total output of all the oxidation energy is simple.

  1. two molecules of ATP gives glycolysis.
  2. oxidation of pyruvate 12 ATP molecules.
  3. 22 molecules falls on the citric acid cycle.

The result: a complete biological oxidation of aerobic way gives energy output equal to 36 molecules of ATP.The value of biological oxidation is obvious.It is this energy is used by living organisms to live and function, as well as to warm his body, movement and other necessary things.

Anaerobic oxidation of a substrate

second type of biological oxidation - anaerobic.That is the one that is carried out at all, but which stops certain types of microorganisms.It glycolysis, and it is here that the differences are clearly seen in the further transformation of substances between aerobic and anaerobic.

stages of biological oxidation in this way are few.

  1. Glycolysis, ie the oxidation of glucose molecules to pyruvate.
  2. fermentation, leading to regeneration of ATP.

Fermentation can be of different types, depending on the organism, its implementing.

Lactic fermentation is carried out by lactic acid bacteria, and some fungi.The point is to restore the STC to lactic acid.This process is used in industry to produce:

  • of dairy products;
  • pickled fruits and vegetables;
  • silage for the animals.

This type of fermentation is one of the most used in human needs.

alcoholic fermentation

known people with the most ancient times.The essence of the process is to convert STC into two molecules of ethanol and two carbon dioxide.Due to such a yield of this type of fermentation used to produce:

  • bread;
  • wine;
  • beer;
  • confectionery and others.

exercising his mushroom yeast and bacterial microorganisms.


Enough narrowly specific type of fermentation.Implemented by bacteria of the genus Clostridium.The bottom line is the conversion of pyruvate into the butyric acid that gives food an unpleasant odor and rancid taste.Therefore

biooxidation reaction going on this path, is practically not used in industry.However, these bacteria inoculated yourself food and harm, lowering their quality.