ABSTRACT
Sodium transport systems serve to maintain ionic balance and cellular transmembrane ionic gradients. Subsequent work involved studies of the quantitative relationship between metabolism and active sodium transport. Primarily, cellular metabolism is necessary to provide energy for the active transport of the solute. Probably the most conclusive evidence showing the Na-K-adenosine triphosphatase (ATPase) to be responsible for active Na and K transport comes from reconstitution of the enzyme system in lipid membrane vesicles. The fundamental principle that underlies the Mitchell chemiosmotic theory is that during the process of respiration, charge separation occurs and thereby creates an electrical and chemical gradient. While the author shall leave the decision as to the validity of these hypotheses to the reader, they should like to leave this subject by stating that the association-induction hypothesis has been seriously attacked on many fronts. Probably one of the most fascinating problems yet to be solved is how the transport systems are regulated.
