What is net movement?

What net movement of a substance occurs in this instance of osmosis?

• Red blood cells have a salt content of 0.9%. When a microbiologist places red blood cells in pure water, osmosis occurs. What net movement of a substance occurs in this instance of osmosis? A. Water molecules move out of the cells. B. Water molecules move into the cells. C. Salt ions move out of the cells. D. Salt ions move into the cells.

• Answer:

  B. Water molecules move into the cells. A cell’s water gain by osmosis is due to a low solute concentration outside the cell. Cells in freshwater swell as the water is drawn toward the higher solute concentration.