The energy exchange that takes place in all cells of a living organism is called dissimilation. It is a set of decomposition reactions of organic compounds, in which a certain amount of energy is released.
Dissimilation takes place in two or three stages, depending on the type of living organisms. So, in aerobes, energy metabolism consists of preparatory, oxygen-free and oxygen stages. In anaerobes (organisms that are able to function in an anoxic environment), dissimilation does not require the last step.
The final stage of energy metabolism in aerobes ends with complete oxidation. In this case, the breakdown of glucose molecules occurs with the formation of energy, which partially goes to the formation of ATP.
It is worth noting that ATP synthesis occurs in the process of phosphorylation, when inorganic phosphate is added to ADP. At the same time, adenosine triphosphoric acid is synthesized in mitochondria with the participation of ATP synthase.
What reaction occurs when this energy compound is formed?
Adenosine diphosphate and phosphate combine to form ATP and a macroergic bond, the formation of which takes about 30.6 kJ /mol. Adenosine triphosphate provides cells with energy, since a significant amount of it is released during the hydrolysis of precisely the macroergic bonds of ATP.
The molecular machine responsible for the synthesis of ATP is a specific synthase. It consists of two parts. One of them is located in the membrane and is a channel through which protons enter the mitochondria. This releases energy, which is captured by another structural part of ATP called F1. It contains a stator and a rotor. The stator in the membrane is fixed and consists of a delta region, as well as alpha and beta subunits, which are responsible for the chemical synthesis of ATP. The rotor contains gamma as well as epsilon subunits. This part spins using the energy of protons. This synthase ensures the synthesis of ATP if the protons from the outer membrane are directed towards the middle of the mitochondria.
It should be noted that chemical reactions in the cell are characterized by spatial order. The products of chemical interactions of substances are distributed asymmetrically (positively charged ions go in one direction, and negatively charged particles go in the other direction), creating an electrochemical potential on the membrane. It consists of a chemical and an electrical component. It should be said that it is this potential on the surface of mitochondria that becomes the universal form of energy storage.
This pattern was discovered by the English scientist P. Mitchell. He suggestedthat substances after oxidation do not look like molecules, but positively and negatively charged ions, which are located on opposite sides of the mitochondrial membrane. This assumption made it possible to elucidate the nature of the formation of macroergic bonds between phosphates during the synthesis of adenosine triphosphate, as well as to formulate the chemiosmotic hypothesis of this reaction.
