AP BIOLOGY

Detailed explanation-1: -In facilitated diffusion, molecules diffuse across the plasma membrane with assistance from membrane proteins, such as channels and carriers. A concentration gradient exists for these molecules, so they have the potential to diffuse into (or out of) the cell by moving down it.

Detailed explanation-2: -In simple diffusion, small noncharged molecules or lipid soluble molecules pass between the phospholipids to enter or leave the cell, moving from areas of high concentration to areas of low concentration (they move down their concentration gradient).

Detailed explanation-3: -The difference between the concentration of a substance in two areas forms a concentration gradient. The rate of diffusion is directly proportional to the concentration gradient. Higher the concentration gradient, the faster the rate of diffusion.

Detailed explanation-4: -The kinetic energy of the molecules results in random motion, causing diffusion. In simple diffusion, this process proceeds without the aid of a transport protein. it is the random motion of the molecules that causes them to move from an area of high concentration to an area with a lower concentration.

Detailed explanation-5: -During diffusion, molecules move from an area where they have a high concentration to areas where they have a low concentration. This process occurs passively without energy expenditure.