Indeed, the ribosomal synthesis of only one peptide bond at a cost of 2 kcal/mol is accompanied by the consumption of four high-energy compounds (ATP, pyrophosphate and 2 GTP), with a total cost of 30 kcal/mol. In addition, the intracellular transport of protein to its workplace and folding of the protein into the working conformation also requires considerable additional energy consumption. The highest energy cost is characteristic of proteins delivered by energy-dependent vesicular transport over huge distances from the body of neurons along axons.

Only now, considering the energy costs underlying the life of cells and the organism as a whole, I realized the high cost of adaptation to the changing conditions of the internal environment of the organism. An example is the activation of the synthesis of a large list of enzymes under hypoxic conditions. For example, hypoxia of cell culture of cytotoxic T lymphocytes leads to an increase in the number of more than 7600 proteins [8]. Considering the huge variety of cells involved in the response to hypoxia, a large amount of the body's energy expenditures for adaptation to hypoxia should be assumed.

In my opinion, it is hypoxia that is the most common cause of changes in cell enzymatic patterns. A feature of hypoxia as a leading pathogenic factor is the high frequency of its manifestation in certain local volumes of organs and tissues. With age, the frequency of episodes of local hypoxia, their duration and depth increase, and, therefore, the expenditure of free energy both for adaptation and for exiting the adapted state and return to normoxia, also accompanied by a change in enzymatic patterns, increases.

The constant implementation of such cycles, initiated by episodes of local or general hypoxia, makes the adaptation process the most energy-consuming process that accelerates aging.

Such operational adaptation of the organism to changes in its internal environment occurs not only at the intracellular level, but also at the level of changes in the ratio of cells, one or another specialization. When it is necessary to survive, the body “puts under the knife” even the cells and tissues that are important for it, using them as a full-fledged, operative endogenous nutrition, completely restoring them in conditions of rest, sleep or anabiosis. Thus, deficient oxygen and free energy are also spent on changes in the cellular composition of the body in the process of adaptation.

In this brief review, I will not consider the expenditure of energy for the work of adaptive mechanisms for the consumption of deficient oxygen at the physiological level, which consists in the redistribution of blood between organs and tissues.

In general terms, adaptation is a positive phenomenon, without which life is impossible. But, adaptation is an energy-consuming process. The pathogenic nature of the operational adaptation constantly going on in the body in the cycle: is due to the large additional costs of energy and, accordingly, oxygen, thereby aggravating hypoxia.

Unlike the operational adaptation to hypoxia that is constantly going on in the body, long-term adaptation to oxygen deficiency, especially from the very beginning of ontogenesis, has an absolutely positive character, which manifests itself in longevity. In the second part of the review, two examples of longevity due to constant hypoxia are considered – the example of the naked mole rat and the example of mountain dwellers.

One of the first results of the constantly occurring adaptive reactions of the body are structural changes accumulating with age in cells, tissues and organs. Signs of aging begin to appear on the connective tissue formations.The system for maintaining homeostasis prevents the accumulation of changes in actively functioning components of cells, and therefore such pathological changes occur and accumulate over time in changes in structural components that are less susceptible to the influence of homeostatic mechanisms. We are talking about changing the content of each of these components or about changing their localization both inside and outside the cells.