Why are gradients important to diffusion and osmosis?
Gradients determine the direction of movement of particles.
Osmosis is a very specific type of diffusion - it is the diffusion of water across a semipermeable membrane.
Both osmosis and diffusion are examples of passive transport in cells. When cells produce carbon dioxide during cellular respiration, it can leave the cell by diffusion through the membrane without the cell needing to use any energy.
Here is a video which discusses the topic of facilitated diffusion and concentration gradients.
And this video discusses how osmosis moves water into or out of cells depending on the concentration gradient.
Hope this helps!