Topic 2A.2 Cell Transport and Diffusion

passive transport

transport that takes place as a result of concentration, pressure or electrochemical gradients and involves no energy from the cell

active transport

the movement of substances into or out of the cell using ATP which is produced during cellular respiration

diffusion

the movement of the particles in a liquid or gas down a concentration gradient from an area where they are at a relatively high concentration to an area where they are at a relatively low concentration

facilitated diffusion

diffusion that takes place through carrier proteins or protein channels

osmosis

a specialised form of diffusion that involves the movement of solvent molecules down their water potential gradient

partially permeable membrane

a membrane which only allows specific substances to pass through it

solute

a substance in a solution, dissolved in the solvent

carrier protein

a protein that moves a substance through the membrane in active transport using energy from the breakdown of ATP or in passive transport such as facilitated diffusion down a concentration gradient

endocytosis

the movement of large molecules into cells through vesicle formation

exocytosis

the movement of large molecules out of cells by the fusing of a vesicle containing the molecules with the surface cell membrane; the process requires ATP