The Location of the Donnan Free Space in Disks of Beetroot Tissue

Abstract

This paper describes experiments which show that the cell walls of beetroot tissue contain sufficient cation·exchange sites to account for at least 95% of the Donnan free space (D.F.S.) as measured by Briggs, Hope, and Pitman (1958). The contribution of the cytoplasm to the D.F.S. in their measurements was therefore less than 5%. The exchange sites in the D.F.S. of the tissue and in the cell walls have the same pKa of about 2·8, and are considered to be due to bound Ilronic acids.