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Unformatted text preview: Movement of Materials in Cells Cells are bathed in a watery matrix and conduct most of their reactions in a similar watery fluid—a solution in which water is the solvent and the numerous molecules and ions dissolved in it are the solutes . The solutes include protons (H + ), ions like sodium (Na + ), potassium (K + ), calcium (Ca 2+ ), organic molecules such as sucrose (C 12 H 22 O 11 ), polar and nonpolar molecules, and a host of other substances, the chemical nature of which determines the ease or difficulty with which they move across membranes. Diffusion All molecules possess kinetic energy and move in a random fashion. In solutions, solutes become distributed uniformly as they diffuse and occupy all available space. Diffusion is the net movement of a substance from a region of its higher concentration to a region of its lower as a result of the...
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This note was uploaded on 11/14/2011 for the course BIO 1421 taught by Professor Farr during the Fall '08 term at Texas State.
- Fall '08