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In page Cell theory:

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In 1956, Afanasy S. Troshin published a book, The Problems of Cell Permeability, in Russian, in which he showed that permeability was of secondary importance in determining the patterns of equilibrium between the cell and its environment. Troshin showed that cell water decreased in solutions of galactose or urea although these compounds did slowly permeate cells. Since the membrane theory requires an impermanent solute to sustain cell shrinkage, these experiments cast doubt on the theory. Others questioned whether the cell has enough energy to sustain the sodium/potassium pump. Such questions became even more urgent as dozens of new metabolic pumps were added as new chemical gradients were discovered.[citation needed]