AEMCA Practice Exam

What is the definition of diffusion?

1. The process where solvent moves to high solute concentration

2. The movement of gas particles from high concentration to lower concentration

3. The active transport of molecules across the cell membrane

4. The absorption of nutrients in the cell

The correct answer is: The movement of gas particles from high concentration to lower concentration

Diffusion is defined as the movement of particles from an area of higher concentration to an area of lower concentration. This process occurs in gases, liquids, and even within solids, as particles naturally spread out to achieve an even distribution. In the context of gases, diffusion is particularly evident as gas particles move freely and randomly, leading to a gradual mixing of different gases in the air until equilibrium is reached. This principle is fundamental in many biological and physical processes, allowing for the exchange of oxygen and carbon dioxide in respiration, for example. While the movement of solvent to areas of high solute concentration pertains to osmosis, which is a specific type of diffusion, it does not capture the broader concept of diffusion itself. Similarly, active transport involves energy expenditure to move substances against their concentration gradient, thus does not define diffusion. Lastly, the absorption of nutrients may involve various mechanisms, including but not limited to diffusion, but it does not encapsulate the essence of diffusion as defined in the context of particle movement across concentrations.