Algonquin College Health Program Assessment (AC-HPAT) Practice Exam

Which transportation method requires energy input?

1. Diffusion

2. Osmosis

3. Active Transport

4. Facilitated Diffusion

The correct answer is: Active Transport

Active transport is the transportation method that requires energy input. This process is essential for moving molecules against their concentration gradient, which means that substances are transported from an area of lower concentration to one of higher concentration. This is contrary to passive transport methods, such as diffusion and osmosis, which occur naturally and do not require additional energy. In active transport, energy is typically derived from ATP (adenosine triphosphate), which provides the necessary power for the transport proteins to function. These proteins often include pumps, like the sodium-potassium pump, that actively move ions in and out of cells, thereby maintaining essential concentrations needed for various cellular functions. In contrast, diffusion and osmosis are natural processes reliant on the kinetic energy of particles and do not require energy input. Facilitated diffusion also occurs along a concentration gradient but utilizes carrier proteins to help transport substances, which still does not require the expenditure of energy. Thus, active transport remains distinct due to its energy dependence, making it essential for processes that maintain homeostasis within cells.