What do you mean by passive and active transport? Write a note on diffusion.

Passive transport: It is the net movement of materials across membranes that does not require any special source of energy.

Active transport: It is a process to transport molecules across the membrane against a concentration gradient. Energy is used in the form of ATP.

Diffusion: Diffusion is the process in which particles move from a region where they are in higher concentration to a region where they are in low concentration, until uniform concentration is finally achieved. Diffusion is faster in the gaseous phase than in liquids and solids.

In unicellular organisms like Amoeba, gaseous exchange takes place through the process of diffusion.