A red blood cell placed in distilled water will

  • A. shrink and become crenated
  • B. remain unchanged
  • C. become turgid but survive
  • D. swell and burst

Explanation

Water enters the cell by osmosis because the cytoplasm has the lower water potential, and with no cell wall to resist the pressure the membrane stretches until it ruptures, a process called haemolysis. Placed in a concentrated salt solution the same cell loses water and becomes crenated instead. This is why fluids given intravenously must be isotonic with blood plasma.

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