OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What happens when a cell is placed in a concentrated sucrose solution?

1. The cell gains water and swells

2. The cell loses water and becomes plasmolysed

3. The cell stays the same size

4. The cell divides and replicates

The correct answer is: The cell loses water and becomes plasmolysed

When a cell is placed in a concentrated sucrose solution, the environment outside the cell has a higher concentration of solutes (sucrose) compared to the inside of the cell. This scenario creates a hypertonic environment relative to the cell's interior. Water molecules will move out of the cell in an attempt to equalize the solute concentrations on either side of the cell membrane. As water leaves the cell, the cell loses volume and can undergo plasmolysis, where the cell membrane pulls away from the cell wall (in plant cells) due to the loss of water. This condition illustrates the principle of osmosis, where water moves from an area of lower solute concentration (inside the cell) to an area of higher solute concentration (outside the cell) until equilibrium is reached. Therefore, a cell placed in a concentrated sucrose solution loses water and becomes plasmolysed, leading to reduced turgor pressure and potential damage to the cell integrity if the concentration difference is too great.