This communication refers to the design and development of an educational material delivered through the Web, concerning the structure of proteins and its relation with their properties and activity. The presentation of the various levels of organization of the proteins' structure has been achieved by means of examples of proteins whose structures are known from X-ray or NMR studies and can be downloaded from databases. The interactive visualization of the structures of macromolecules has been done with the aid of the Jmol application based on the Java machine. The presentation of each topic covered has been implemented with an educational scenario in which the crucial structural characteristics of the example protein structure evolve after certain actions of the student.