Question

what is the difference between diffusion and active transport

Answer 1

Diffusion Occurs along the conc. gradient while active transport occurs against the conc. gradient.
Diffusion is passive whereas Active transport is Active Process i.e. require ATP

Answer 2

Also: diffusion does not require the cell to use energy (ATP) while active transport needs added energy.

Answer 3

You can have active transportation with concentration gradients if the cell needs to speed up the rate of movement.

Answer 4

@BioEpic is most correct, the cell expends energy in active transport and does not in simple diffusion (passive) transport.