Ohio Assessment for Educators (OAE) Integrated Science (024) Practice Exam

What process describes the movement of molecules from an area of high concentration to an area of low concentration?

1. Passive transport

2. Active transport

3. Facilitated diffusion

4. Endocytosis

The correct answer is: Passive transport

The movement of molecules from an area of high concentration to an area of low concentration is known as passive transport. This process relies on the natural tendency of substances to move down their concentration gradient without the need for energy input. In the context of passive transport, particles move spontaneously, which is a fundamental concept in biology that reflects how substances achieve equilibrium within a solution or across a membrane. This movement occurs until the concentrations on both sides of a membrane reach relative balance, known as equilibrium. The other options represent different processes that involve movement across membranes but require a different context or energy source: active transport moves molecules against their concentration gradient and requires energy, facilitated diffusion involves the use of protein channels and, while it is still a passive process, it is specific to certain types of molecules, and endocytosis involves the engulfing of substances by the cell membrane, which also requires energy. Thus, passive transport stands out as the process directly described in the question, focused solely on the movement toward lower concentration areas.