The course addresses computer-based calculations within chemistry. The course integrates theory with practical computation elements applied within the fields of environmental chemistry, protein chemistry and medicinal chemistry. The students are expected to acquire knowledge within quantum chemistry, molecular mechanics, bioinformatics, and the theoretical characterisation of molecules, and applied methods for computation of the geometric and electronic structure of molecules. The course comprises both theory and practical application of important concepts within quantum chemistry and molecular mechanics. Central concepts for the computer-based application of organic molecules within quantum chemistry will be described and discussed. The focus within molecular mechanics is on describing and discussing the practical application of organic molecules, including proteins. The bioinformatics part of the course addresses the construction and use of databases containing biological information, protein sequence comparisons and 3D structure comparisons. The theory behind methods, practical execution and assessment of the quality of the sequence comparison are addressed and discussed. The theoretical characterisation of molecules interconnects the various sections of the course, i.e., quantum chemistry, molecular mechanics and bioinformatics.