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Unformatted text preview: Movement of Substances There are a few concepts that need to be understood relating to the movement of substances. The movement of substances may occur across a semi-permeable membrane (such as the plasma membrane). A semi-permeable membrane allows some substances to pass through, but not others. The substances, whose movements are being described, may be water (the solvent) or the substance dissolved in the water (the solute). Movement of substances may occur from higher to lower concentrations (down the concentration gradient) or from the opposite direction (up or against the gradient). Solute concentrations vary. A solution may be hypertonic (a higher concentration of solutes), hypotonic (a lower concentration of solutes), or isotonic (an equal concentration of solutes) compared to another region. The movement of substances may be passive or active. If movement is with the concentration or The movement of substances may be passive or active....
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- Spring '10