Why are gradients important in diffusion and osmosis?
If osmosis and diffusion move along the concentration gradient it is known as passive diffusion. Passive diffusion/osmosis is when molecules/water move through a selectively permeable membrane from an area of high to low concentration. Passive diffusion requires no energy.
However if diffusion occurs against the concentration gradient it is known as active diffusion. Active diffusion is when molecules move through a selectively permeable membrane from an area of low to high concentration. Active diffusion requires carrier proteins and cellular energy.
Here is a video which describes how osmosis impacts onion cells placed into tap water and then into a salt water solution.
Hope this helps!