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 “active” because it requires an input of energy to move molecules against (up) their concentration gradient. Neither simple nor facilitated diffusion (both examples of passive transport) require energy because both allow molecules to move along (down) their concentration gradient.

Detailed explanation-3: -Active transport requires energy to move substances across a plasma membrane, often because the substances are moving from an area of lower concentration to an area of higher concentration, or because of their large size.

Detailed explanation-4: -To move materials against the concentration gradient (from an area of lower concentration to an area of higher concentration), cells need to use energy. This energy required to move molecules is obtained from ATP, which is generated through cellular metabolism.

Detailed explanation-5: -Concentration gradient refers to the change that occurs when molecules diffuse across the membrane. Basically, the concentration of two molecules differs from both sides of the membrane. The cell is often trying to reach the concentration gradient to an equilibrium state.