Biochemical Foundations of Human Vital Activity - Volkov, N.I., Nesen, E.N. 2000

Biochemical Foundations of Human Vital Activity
Metabolism in the Body
Catabolic and anabolic reactions: two sides of metabolism

METABOLISM comprises two interconnected yet opposing processes: anabolism and Catabolism (Fig. 7).

Anabolism (assimilation) involves the synthesis of complex chemical substances from simpler molecules. This process yields Nucleic Acids, Proteins, and other macromolecular Components of the Organism. This facet of metabolism also encompasses The breakdown of nutrients during Digestion, as this supplies Cells with the building blocks and energy required for anabolic pathways. Anabolic reactions proceed with the utilization of chemical energy in the form of ATP or NADH₂.

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Fig. 7 Interrelation between anabolic and catabolic metabolic processes

Catabolism (dissimilation) refers to the breakdown of complex substances within body cells into simpler compounds or low-molecular-weight end products (such as CO₂, H₂O, and NH₃) that are subsequently excreted from the body. Catabolic reactions are accompanied by the release of Free energy stored within the complex molecules of Organic compounds. A portion of this energy is converted into chemical energy (such as ATP and NADH₂) and stored within the cells, while the greater part is dissipated as heat.

Although anabolism and catabolism are opposing processes that occur independently of one another, they are closely interrelated. Catabolic processes supply metabolites and energy for anabolic pathways, whereas anabolic reactions build up and store complex nutrients and energy, thereby Setting the Stage for subsequent catabolic reactions (see Fig. 7).

The rate and balance of anabolic and catabolic processes depend on numerous factors, primarily a person's age and physical activity. In children, for instance, anabolic processes predominate over catabolic ones, establishing the conditions necessary for bodily growth and Muscle mass accumulation. Because anabolic processes demand significant Energy Expenditure, children are advised against heavy and prolonged physical exertion, which could potentially impair growth processes.

After the age of 17–20, once growth ceases, metabolic balance is established, much like in adults. The adult body is characterized by a dynamic equilibrium between synthesis (anabolism) and breakdown (catabolism), which is reflected in the relative constancy of body weight.

In the Aging organism, catabolic processes prevail, leading to a decline in structural proteins, Enzymes, Hormones, and other functionally vital substances. Consequently, the body's speed-strength capabilities, adaptability, and recovery capacity following physical exertion diminish. For this reason, the aging body tolerates maximal physical loads—particularly strength-based ones—poorly. Nevertheless, moderate physical activity enhances metabolic intensity and prolongs the period of high functional capacity.

An imbalance between anabolic and catabolic processes is observed in various diseases, poor Nutrition, exposure to adverse environmental factors, excessive physical exertion, and improper training Organization.

Physical activity increases the overall metabolic rate, markedly intensifying catabolic processes in skeletal Muscles and other Tissues to supply energy to working muscles. Meanwhile, The rate of anabolism decreases due to energy deficits.

During the recovery period following physical work, both processes operate intensively. Their balance is restored only after Protein Biosynthesis has recovered, which can take anywhere from 12 to 24 hours depending on The Nature of the physical activity performed. Therefore, in sports practice, Protein metabolism metabolites are analyzed to characterize an athlete's post-training recovery.

During the recovery phase following physical exertion, an excessive accumulation of certain energy substrates and protein compounds occurs, a phenomenon known as supercompensation. This adaptive capacity of metabolism creates conditions for enhancing the body's functional capabilities and improving physical fitness through athletic training.