AP BIOLOGY

Detailed explanation-1: -During active transport, substances move against the concentration gradient, from an area of low concentration to an area of high concentration. This process is “active” because it requires the use of energy (usually in the form of ATP). It is the opposite of passive transport.

Detailed explanation-2: -Active transport is the transport of molecules that require the use of energy, in the form of an energy-storing chemical called ATP (adenosine triphosphate) to help them cross the cell membrane.

Detailed explanation-3: -ATP plays a critical role in the transport of macromolecules such as proteins and lipids into and out of the cell. The hydrolysis of ATP provides the required energy for active transport mechanisms to carry such molecules across a concentration gradient.