Explain the differences between diffusion, osmosis and active transport.

Diffusion, osmosis, and active transport are three distinct processes that are essential for the movement of molecules across cellular membranes. Here are the differences between these processes:

1. Diffusion: Diffusion is the process by which molecules move from an area of high concentration to an area of low concentration, until equilibrium is reached. This movement occurs due to the random motion of the molecules and does not require energy. Diffusion can occur across a semi-permeable membrane or in a solution.
2. Osmosis: Osmosis is a specific type of diffusion that involves the movement of water molecules from an area of high concentration to an area of low concentration, across a semi-permeable membrane. Like diffusion, osmosis does not require energy.
3. Active transport: Active transport is the movement of molecules against their concentration gradient, from an area of low concentration to an area of high concentration. This process requires energy in the form of ATP (adenosine triphosphate) and the help of membrane-bound transport proteins. Active transport is important for maintaining concentration gradients and for moving molecules into or out of cells when diffusion or osmosis is not sufficient.

Overall, while all three processes involve the movement of molecules across cellular membranes, they differ in their mechanisms, the type of molecules involved, and whether or not energy is required.