Can someone please explain to me the enzyme-substrate complex?Watch
A change in the enzyme's environment (the substrate colliding into it) results in a change in the enzymes shape and so the enzyme active site changes shape too, and therefore 'grasps' the substrate (binds to it).
The enzyme-substrate complex is formed via random collisions between the enzymes and substrate molecules. A certain amount of energy is needed to allow these to effectively bind and form the enzyme-substrate complex. Similarly, they must collide with the correct orientation (facing one another the correct way). The active site is specific to one substrate and so can only bind effectively and work upon a particular substrate.