The 2 GIFs above show a life-like animation of the Electron Transport Chain & ATP Synthase
Diffusion describes the tendency of materials (solutes in particular) to want to move from areas of high concentration to areas of low concentration.
In the world of cells, often what is separating different solutions is the cell membrane made of a lipid bilayer and various different proteins.
Enzymes bind to specific substrates. The substrate fits into the enzyme at a location on the enzyme called the active site.
Some enzymes break down substrates into smaller molecules.
Other enzymes link two or molecules into larger or different molecules.
Enzymes make biological reactions happen faster.