[en] Full text: Embedding molecules in helium clusters has become a powerful technique for the preparation of cold targets for spectroscopy experiments, as well as for the assembly of complex, fragile molecular species. In order to gain further insight into the role of secondary-electron interactions for radiation damage at a molecular level, we investigated simple amino acids like glycine and valine in He droplets as well as acetic acid. The latter molecule is of special importance, as it is a building block of the amino acids. The present measurements are performed with a He cluster source, a pick-up chamber containing the vapor of the biomolecule and a double focusing mass spectrometer. Ultra-cold superfluid He droplets (0.37 K) can easily pick up gas phase biomolecules to form complex targets which can be probed via electron attachment and electron impact ionization. By comparison with the results for the isolated molecules in gas phase, effects by the surrounding matrix can be easily deduced. Experimental results for positive and negative ion formation of He droplets doped with the above mentioned organic acids are shown. For a better understanding of the ongoing processes we carry out quantum-chemical calculations. Molecular properties which are of interest for these experiments are the total energies of the molecules and the energies of the reactions. Furthermore we calculate the electron affinity as well as the salvation energies. (author)