Humber Admissions Practice Test

What is active transport?

1. The movement of materials from high to low concentration

2. The use of energy to move materials from low to high concentration

3. Transport of molecules without energy usage

4. The exchange of gases across a membrane

The correct answer is: The use of energy to move materials from low to high concentration

Active transport is the process in which substances are moved across a cell membrane against their concentration gradient, from an area of lower concentration to an area of higher concentration. This movement requires the input of energy, usually in the form of ATP, because it is working against the natural tendency for substances to move from areas of high concentration to areas of low concentration. Understanding that active transport is energy-dependent distinguishes it from passive transport mechanisms, which do not require energy and involve movement down a concentration gradient. This is why the use of energy to facilitate the movement of materials from low to high concentration is the defining feature of active transport. The other options describe different transport mechanisms or processes that do not accurately reflect the characteristics of active transport.