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 pK[alpha] of about 2.8, and are considered to be due to bound uronic acids.