Final answer:
Water passes quickly through cell membranes because it moves through transmembrane proteins or channels called aquaporins.
Step-by-step explanation:
Water passes quickly through cell membranes because it moves through transmembrane proteins or channels called aquaporins. These aquaporins act as selective channels that allow water molecules to move freely while blocking the passage of other molecules. The movement of water through aquaporins is facilitated by osmosis, which is the diffusion of water across a selectively permeable membrane. This allows cells to regulate their water balance efficiently and maintain proper hydration.
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