Qualified Medication Aides (QMA) Practice Exam

Which of the following best describes osmosis?

1. Movement of water from low to high solute concentration

2. Movement of solute from high to low solute concentration

3. Equal distribution of solute in solutions

4. Active transport of molecules against a gradient

The correct answer is: Movement of water from low to high solute concentration

Osmosis is specifically defined as the movement of water across a selectively permeable membrane from an area of low solute concentration to an area of high solute concentration. This process occurs in order to achieve equilibrium, or balance, between the solute concentrations on either side of the membrane. Water moves to dilute the area with a higher concentration of solute until the concentrations become equal. The other options do not accurately capture the essence of osmosis. Movement of solute from high to low concentration refers to diffusion, which is a different process. Equal distribution of solute in solutions signifies a state of equilibrium rather than the process of osmosis itself. Active transport refers to the movement of molecules against their concentration gradient, which requires energy, contrasting with the passive nature of osmosis that does not require energy input. Therefore, the clarity of the definition provided in the correct answer reinforces the essential concept of osmosis in cellular biology.