This book is designed for students of biology, molecular biology, ecology, medicine, agriculture, forestry and other professions where the knowledge of organic chemistry plays the important role. The work may also be of interest to non-professionals, as well as to teachers in high schools. The book consists of 11 chapters that cover: - basic principles of structure and constitution of organic compounds, - the elements of the nomenclature, - the concepts of the nature of chemical bond, - introductions in NMR and IR spectroscopy, - the concepts and main classes of the organic reaction mechanisms, - reactions and properties of common classes or organic compounds, - and the introduction to the chemistry of the natural organic products followed by basic principles of the reactions in living cells.