AP BIOLOGY

Detailed explanation-1: -In active transport, unlike passive transport, the cell expends energy (for example, in the form of ATP) to move a substance against its concentration gradient.

Detailed explanation-2: -There are two major ways that molecules can be moved across a membrane, and the distinction has to do with whether or not cell energy is used. Passive mechanisms like diffusion use no energy, while active transport requires energy to get done.

Detailed explanation-3: -The simplest forms of transport across a membrane are passive. Passive transport does not require the cell to expend any energy and involves a substance diffusing down its concentration gradient across a membrane.

Detailed explanation-4: -Active transport uses cellular energy, unlike passive transport, which does not use cellular energy. Active transport is a good example of a process for which cells require energy.

Detailed explanation-5: -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.