Extracellular osmotic activity accumulation capacity

Further support comes from the studies relating cell wall biosynthesis and amino acid accumulation capacity in vitamin B6-deficient cells, since it is difficult to account for these observations without attributing considerable osmotic activity to the accumulated amino acids. Any description of accumulation which invokes amino acid attachment to intracellular binding sites, whose affinity can be reduced by a vitamin B6 deficiency, must account for the stimulation of uptake that accompanies the synthesis of essentially extracellular cell wall material. If the reduction in affinity occurs because the cell interior becomes overhydrated (a reasonable postulate which follows from the osmotic experiments), the beneficial effect of wall synthesis is not readily explicable, since vitamin B6-deficient cells have a swollen appearance which is not significantly altered after wall synthesis has been stimulated. Thus, the existing overhydration within the cell probably is not reversed by this change. In contrast, the deposition of additional wall substance would prevent further unfavorable consequences of swelling such as membrane distention, and, in this way, forestall the premature cessation of amino acid accumulation. 

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