The textbook discusses the main provisions of classical biological chemistry, provides information on the structure and properties of molecules of the human body, the molecular foundations of human physiological functions. Biochemical features of the most important organs and tissues are considered. Modern ideas about the molecular foundations of some of the most common pathological conditions are presented. The textbook includes situational tasks and tests that provide students with active study of the material. The textbook is intended for students of medical and pharmaceutical universities, graduate students and teachers of biological chemistry.