AP BIOLOGY

Detailed explanation-1: -In passive transport, particles will diffuse down a concentration gradient, from areas of higher concentration to areas of lower concentration, until they are evenly spaced.

Detailed explanation-2: -The direction of diffusion is said to be ‘down’ or ‘with’ the concentration gradient. Diffusion stops when the concentration of the substance is equal in both areas. This does not mean that the molecules of substance are not moving any more, just that there is no overall movement in one direction.

Detailed explanation-3: -The term concentration gradient is an important one. Although the word gradient sugggests height, it in fact refers to amount: that is, particles move from where there are many, to where there are few. So the gradient is the direction from lots to less.

Detailed explanation-4: -Molecules are said to naturally flow down their concentration gradient. This type of diffusion proceeds without an input of energy. In simple diffusion, molecules that are small and uncharged can freely diffuse across a cell membrane. They simply flow through the cell membrane.

Detailed explanation-5: -A concentration gradient is the difference in concentration of a substance from one location to another. A molecule diffuses down its concentration gradient by moving from one region of higher concentration to a region of lower concentration.