Simple diffusion – Movement of molecules along the concentration gradient of molecules without any requirement of energy. (some glucose, amino acids, chloride ions).
Active transport – Movement of molecules across semipermeable membrane against the concentration gradient requiring energy from ATP (amino acids, glucose, sodium).
Facilitated Diffusion: Diffusion of some ions and polar molecules across membranes through special transport proteins (fructose and some amino acids).
Osmosis: Movement of water molecules across semi permeable membrane from a region of their higher concentration to a region of their lower concentration (transport of water).