Translationally active cell-free systems from gills of the Antarctic scallop Adamussium colbecki (Smith 1902) and the European scallop Aequipecten opercularis (Linnaeus 1758) were developed, characterised and optimised for an analysis of translational capacity. The aim was to determine the energetic cost of protein synthesis in the in vitro cell free system by directly measuring the required energy equivalents in the lysates. Protein synthesis rate in assays conducted with lysates of A. colbecki (1,029±0,061 µmol Phe/min at 15 °C) were higher compared to lysates of A. opercularis (0,087±0,013 µmol Phe/min at 15 °C and 0,156±0,023 µmol Phe/min at 25 °C). This can in part be attributed to the naturally occurring higher RNA content in lysates of A. colbecki (0,883±0,037 mg RNA/ml lysate) compared to A. opercularis (0,468±0,013 mg RNA/ml lysate).There was no significant difference in the energetic costs of protein synthesis in cell free systems of gill lysates of the cold stenothermal A. colbecki with 4,3±0,7 energy equivalents/peptide bond formed and the eurythermal A. opercularis with 5,6±0,6 energy equivalents, indicating that there are no differences in the efficiency of the translation machinery. The energetic costs specified for protein synthesis correspond with the generally accepted theoretical value of 4 energy equivalents per peptide bond formed, especially in gill lysates of A. colbecki, whereas the value for gill lysates of A. opercularis was slightly higher.