Any our movement or thought requires energy from the body. This cell is stored in each cell of the body and accumulates it in biomolecules with the help of macroergic bonds. It is these battery molecules that provide all the vital processes. The constant exchange of energy within the cells determines life itself. What are these biomolecules with macroergic bonds, where they come from, and what happens to their energy in every cell of our body - this is discussed in the article.
Biological intermediaries
In any organism, energy does not directly transfer from an energy-generating agent to a biological energy consumer. When breaking intramolecular bonds of food products, the potential energy of chemical compounds is released, far exceeding the ability of intracellular enzymatic systems to use it. That is why in biological systems the release of potential chemicals occurs stepwise with their phased conversion into energy and its accumulation in macroergic compounds and bonds. And it is biomolecules that are capable of such energy storage that are called high-energy.
What relationships are called macroergic?
The free energy level of 12.5 kJ / mol, which is formed during the formation or decomposition of a chemical bond, is considered normal. When the formation of free energy of more than 21 kJ / mol occurs during the hydrolysis of certain substances, this is called macroergic bonds. They are indicated by the symbol "tilde" - ~. Unlike physical chemistry, where macroergic bonding refers to covalent bonding of atoms, in biology they mean the difference between the energy of the starting agents and their decay products. That is, energy is not localized in a specific chemical bond of atoms, but characterizes the whole reaction. In biochemistry, they talk about chemical conjugation and the formation of a macroergic compound.
Universal bioenergy source
All living organisms on our planet have one universal element of energy storage - this is the macroergic linkage of ATP - ADP - AMP (adenosine tri, di, monophosphoric acid). These are biomolecules that consist of a nitrogen-containing adenine base attached to the ribose carbohydrate and attached phosphoric acid residues. Under the action of water and the restriction enzyme, the adenosine triphosphoric acid molecule (C 10 H 16 N 5 O 13 P 3 ) can decompose into adenosine diphosphoric acid molecule and orthophosphate acid. This reaction is accompanied by the release of free energy of the order of 30.5 kJ / mol. All vital processes in each cell of our body occur during the accumulation of energy in ATP and its use when breaking bonds between residues of phosphoric acid.
Donor and Acceptor
Macroergic compounds also include substances with long names that can form ATP molecules in hydrolysis reactions (for example, pyrophosphoric and pyruvic acids, succinyl coenzymes, aminoacyl derivatives of ribonucleic acids). All these compounds contain phosphorus (P) and sulfur (S) atoms, between which there are high-energy bonds. It is the energy that is released upon breaking the macroergic bond in ATP (donor) that is absorbed by the cell in the synthesis of its own organic compounds. And at the same time, the reserves of these bonds are constantly replenished during the accumulation of energy (acceptor) released during the hydrolysis of macromolecules. In each cell of the human body, these processes occur in the mitochondria, while the duration of ATP is less than 1 minute. For a day, our body synthesizes about 40 kilograms of ATP, which undergo up to 3 thousand decay cycles each. And at every single moment in our body there is about 250 grams of ATP.
The functions of high-energy biomolecules
In addition to the functions of the donor and acceptor of energy during the decay and synthesis of high molecular weight compounds, ATP molecules play several more very important roles in cells. The energy of breaking macroergic bonds is used in the processes of heat generation, mechanical work, the accumulation of electricity, glow. At the same time, the conversion of the energy of chemical bonds into thermal, electrical, and mechanical simultaneously serves as a stage of energy exchange with subsequent storage of ATP in the same macro-energy bonds. All these processes in the cell are called plastic and energy exchanges (diagram in the figure). ATP molecules also act as coenzymes, regulating the activity of certain enzymes. In addition, ATP can also be a mediator, a signaling agent in the synapses of nerve cells.
The flow of energy and matter in the cell
Thus, ATP in the cell occupies a central and main place in the exchange of matter. The reactions by which ATP occurs and decomposes are quite numerous (oxidative and substrate phosphorylation , hydrolysis). Biochemical reactions of the synthesis of these molecules are reversible, under certain conditions they are shifted in the cells towards synthesis or decay. The paths of these reactions differ in the number of transformations of substances, the type of oxidative processes, and the methods of pairing energy-supplying and energy-consuming reactions. Each process has clear adaptations to the processing of a specific type of “fuel” and its own limits of efficiency.
Efficiency mark
The efficiency indicators of energy conversion in biosystems are small and are estimated in standard values of the coefficient of efficiency (the ratio of useful, spent on the work, to the total energy used). But, to ensure the implementation of biological functions, the costs are very large. For example, a runner, in terms of unit mass, spends as much energy as a large ocean liner. Even at rest, maintaining the body’s life is hard work, and it takes about 8 thousand kJ / mol. At the same time, about 1.8 thousand kJ / mol is spent on protein synthesis, 1.1 thousand kJ / mol on the heart, but up to 3.8 thousand J / mol on ATP synthesis.
Adenylate Cell System
This is a system that includes the sum of all ATP, ADP and AMP in a cell in a specific time period. This value and the ratio of components determines the energy status of the cell. The system is evaluated by the indicator of the energy charge of the system (the ratio of phosphate groups to the adenosine residue). If in the cell macroergic compounds are represented only by ATP - it has the highest energy status (indicator -1), if only AMP - the minimum status (indicator - 0). In living cells, usually 0.7-0.9 are maintained. The stability of the energy status of the cell determines the rate of enzymatic reactions and support the optimal level of vital activity.
And a little about power stations
As already mentioned, the synthesis of ATP occurs in specialized cell organelles - mitochondria. And today, biologists are debating about the origin of these amazing structures. Mitochondria are cell power plants, for which are proteins, fats, glycogen, and electricity is ATP molecules, the synthesis of which takes place with the participation of oxygen. We can say that we breathe so that mitochondria work. The more work cells must do, the more energy they need. Read - ATP, which means mitochondria.
For example, a professional athlete in the skeletal muscles contains about 12% of mitochondria, and an unsportsmanlike inhabitant has half their number. But in the heart muscle, their indicator is 25%. Modern training techniques for athletes, especially marathon runners, are based on indicators of MCP (maximum oxygen consumption), which directly depends on the number of mitochondria and the ability of muscles to perform long-term loads. Leading training programs for professional sports are aimed at stimulating the synthesis of mitochondria in muscle cells.