Plan
► Concept of metabolism in human and animal organism. Sources of energy in organism.
► General concepts and definitions of physiology of metabolism.
► Methods of study of energy metabolism in human.
► Concept of rational diet.
Concept of Metabolism in Organism. Sources of Energy in Organism
A human organism is an open thermodynamic system characterized by metabolism.
Metabolism is a complex of physical, biochemical and physiological transformations of substances and energy in a human organism and exchange of substances and energy between an organism and the environment. These processes occurring in a human organism are studied by many sciences: biophysics, biochemistry, molecular biology, endocrinology and physiology.
Metabolism and energy exchange are closely interrelated, but for the sake of simplicity they are studied separately.
Metabolism is a complex of chemical and physical transformations that occur in the body and ensure its viability in interactions with the environment.
In the body two oppositely directed processes occur: assimilation and dissimilation.
Assimilation (anabolism) is a complex of processes directed at construction of the living matter. Constructive processes consume energy.
Dissimilation (catabolism) is a complex of processes that break down the living matter. Breakdown processes produce energy.
Life of animals and humans is a unity of assimilation and dissimilation processes that are coupled by two systems:
► ATP - ADP (ATP - adenosine triphosphate; ADP - adenosine di-phosphate);
► NADP (oxidized) - NADPH (reduced); (NADP - nicotine amide adenine dinucleotide phosphate).
These processes are coupled by ATP and NADP molecules, which function as universal accumulators and carriers of energy. But before the energy is accumulated in ATP and NADP molecules it must be obtained from nutrients which enter an organism with food. These nutrients are proteins, fats and carbohydrates. It should be said that nutrients not only supply energy, but also serve as material for construction of cells, tissues and organs (plastic function). Different nutrients play different roles in meeting plastic and energetic demands of an organism. Carbohydrates primarily perform energetic function, their plastic function is negligible. Fats perform both energetic and plastic functions to the equal extent. Proteins are the basic building material in the body, but under certain conditions they may serve as a source of energy.