Question

What is osmosis (and how is it different to diffusion and active transport) ?

Answer 1

Osmosis is diffusion of water

Explanation:

Osmosis is the diffusion/movement of water from a high to low concentration of water through a semi-permeable membrane (i.e. down a concentration gradient). So requires no energy to occur.
A semi-permeable membrane only allows small molecules (in this case, water) to pass through, so large molecules such as sugar cannot pass.

Active transport is the net movement of molecules/particles from a low to high concentration (i.e. up a concentration gradient) and so requires energy for this to occur.