Maintenance of Cell Volume

At an early stage of evolution, before the development of cells, life might well have been nothing more than a loose confederation ofenzyme systems and self-replicating molecules. A major problem faced by such acellular systems must have been how to keep their constituent parts from simply diffusing away into the surrounding murk. The solution to this problem was the development of a cell membrane that was impermeable to the organic molecules. This was the origin of cellular life. However, the cell membrane, while solving one problem, brought with it a new problem: how to achieve osmotic balance. To see how this problem arises, it will be useful to begin with a review of solutions, osmol-arity, and osmosis. We will then turn to an analysis of the cellular mechanisms used to deal with problems of osmotic balance.

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