Which of the following statements about osmosis is correct?
a. If a cell is placed in an isotonic solution, more water will enter the cell than leaves the cell.
b. Osmotic movement of water into a cell would likely occur if the cell accumulates water from its environment.
c. The presence of aquaporins (proteins that form water channels in the membrane) should speed up the process of osmosis.
d. If a solution outside the cell is hypertonic compared to the cytoplasm, water will move into the cell by osmosis.
e. Osmosis is the diffusion of water from a region of lower water concentration to a region of higher water concentration.
The Correct Answer and Explanation is:
The correct answer is c. The presence of aquaporins (proteins that form water channels in the membrane) should speed up the process of osmosis.
Explanation:
Osmosis is the process by which water molecules move across a selectively permeable membrane from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration). This movement occurs to balance solute concentrations on both sides of the membrane and maintain homeostasis.
Aquaporins, which are specialized protein channels embedded in the cell membrane, play a crucial role in facilitating this water movement. Without aquaporins, water can still diffuse through the cell membrane, but the process is much slower due to the hydrophobic nature of the lipid bilayer. Aquaporins significantly speed up the process of osmosis by allowing water molecules to pass through the membrane more efficiently and in larger quantities. This is especially important in cells that require rapid water regulation, such as kidney cells and red blood cells.
Let’s review why the other statements are incorrect:
- Option a: In an isotonic solution, the solute concentration is equal inside and outside the cell. Thus, water moves equally in both directions, and there is no net water movement into or out of the cell. Therefore, more water does not enter the cell than leaves it.
- Option b: Water moves based on solute concentration gradients, not because the cell “accumulates” water. The movement would occur only if the cell’s internal solute concentration is higher than that of the external environment.
- Option d: In a hypertonic solution, the solute concentration outside the cell is higher than inside. Water would move out of the cell, not into it, to balance the concentrations.
- Option e: Osmosis involves water moving from a region of higher water concentration to lower water concentration, not the other way around. Therefore, this statement is incorrect.
Thus, the correct answer is that aquaporins speed up the process of osmosis.