movement of substances

define diffusion

the net movement of particles down a concentration gradient (until equilibrium is reached)

describe the role of diffusion in nutrient uptake and gaseous exchange in plants and humans

define osmosis

the net movement of water molecules from a region of higher water potential to a region of lower water potential through a selectively permeable membrane

describe the effects of osmosis on plants and animal tissues

define active transport

the process where cellular energy, in the form of adenosine triphosphate (ATP), is used to move the particles of a substance across a membrane against its concentration gradient

discuss the importance of active transport

it is an energy-consuming process by which substances are transported against a concentration gradient, as in ion uptake by root hairs and uptake of glucose by cells in the villi

explain how different substances move across membranes through simple diffusion