The second block of the syllabus is devoted to describing the composition, structure and properties of biomolecules and to lay the foundations of the relationship between the structure of biomolecules and their biological function. The block begins with the study of the properties of water as the main solvent in biological processes. After, the tnext unit is dedicated to the study of carbohydrates, starting with simple sugars and then moving on to more complex structures. We describe the chemical composition, types and functions of nucleic acids, prior to the analysis of structural organization. It examines the characteristics of amino acids, especially their hydrophobicity, size and acid-base. then, it is explainedhow the peptide bond defines the concept of rotation of link and the differences between configuration and conformation are established. We analyze the three-dimensional structures of fibrous and globular proteins and provide an overview of knowledge about the mechanism of protein folding. It approaches the study of lipids, which begins with simple lipids and fatty acids and triacylglycerols, and continues with the more complex lipids such as phospholipids and sphingolipids. Finally we describe the main features of biological membranes, its components, the assembly mechanism and thermodynamics of formation in aqueous media.