AP BIOLOGY

Detailed explanation-1: -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-2: -Diffusion. Diffusion is a passive process of transport. A single substance tends to move from an area of high concentration to an area of low concentration until the concentration is equal across the space.

Detailed explanation-3: -Concentration Gradient and Diffusion The particles may move along or against their concentration gradient. The downhill movement of particles is called passive transport (e.g. simple diffusion). Conversely, the uphill movement is referred to as active transport.

Detailed explanation-4: -Passive transport, most commonly by diffusion, occurs along a concentration gradient from high to low concentration. No energy is necessary for this mode of transport.

Detailed explanation-5: -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.