At the Chair of Biochemistry II, mass spectrometric analysis is used to answer biological questions from the molecular to the cellular level. Central questions are the biogenesis of the proteome of mitochondria and peroxisomes and the integration of these vital organelles into larger signalling networks in yeast and human cells. In a complementary branch of research, we systematically investigate protein kinase- and protein phosphatase-dependent signalling networks to elucidate signalling processes involved in protection against mechanical stress.