The study of Euclidean Steiner Trees is one of the alternative methods to unveil Nature's plans for the internal architecture of biomacromolecules. Recently, the minimum surface structure of the A-DNA and of the Tobacco Mosaic Virus was shown to be described by a "strake" surface. These results have been substantiated by an explicit calculation of the Steiner Ratio Function in a very restrictive modelling scheme. In the present work, we also introduce the measure of chirality as an essential part of a thermodynamical approach to model biomolecular structure. In a certain sense, the Steiner Ratio function is constrained by the chirality measure to assume a value dictated by Nature. This value is a measure of the free energy of the molecular configuration.