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

What is the primary factor that causes water to move into a cell?

1. Temperature differences

2. Lower pressure inside the cell

3. Higher concentration of water outside the cell

4. Higher concentration of solutes inside the cell

The correct answer is: Higher concentration of solutes inside the cell

Water moves into a cell primarily due to osmosis, which is the movement of water across a selectively permeable membrane in response to differences in solute concentration. When there is a higher concentration of solutes inside the cell, it creates a less concentrated environment compared to the outside. Therefore, water moves from an area of higher water concentration (outside the cell) to an area of lower water concentration (inside the cell) to help equalize the solute concentrations. This process is driven by the tendency of water to dilute solutes until equilibrium is reached. If there are more solutes inside the cell, then more water will be drawn into the cell to balance the concentration difference. Thus, the higher concentration of solutes inside the cell is the primary factor causing water to move in, highlighting the role of osmosis in cellular function.