Question

multiple choice 5 points
the cells from a leaf of an elodea plant growing in a freshwater aquarium will shrink when placed in a hypertonic solution containing 8% salt. which statement best explains why the cells shrink?
water moves from the cytoplasm of the cell into the nucleus
salt moves from the hypertonic solution into the cell and binds chemically with water.
salt causes the cell membrane to swell and absorb water from the cytoplasm.
water moves from the cell through the cell membrane to an area of lower water concentration.

Explanation:

Osmosis is the movement of water across a semi - permeable membrane from an area of higher water concentration to an area of lower water concentration. In a hypertonic solution (a solution with a higher solute concentration compared to the cell's cytoplasm), the water concentration outside the cell is lower than inside the cell. So, water moves out of the cell (from the cell through the cell membrane to an area of lower water concentration) to balance the concentration gradient, causing the cell to shrink.

• The second option is incorrect because salt does not cause the cell membrane to swell and absorb water. In a hypertonic solution, water moves out of the cell.
• The third option is incorrect. In a hypertonic solution, water moves out of the cell, not salt moving into the cell. Also, salt does not bind chemically with water in this context of cell shrinkage due to osmosis.
• The fourth option is incorrect. Water does not move from the cytoplasm of the cell into the nucleus during cell shrinkage due to being in a hypertonic solution. The movement is across the cell membrane to the outside of the cell.

Answer:

Water moves from the cell through the cell membrane to an area of lower water concentration.