The functioning of the enzyme is determined by the shape of the protein. It recognizes, confines and orients the substrate in a particular direction. Space filling model of an enzyme working on glucose. Image from W.H. Freeman and Sinauer Associates, used by permission. The induced fit hypothesis suggests that the binding of the substrate to the enzyme alters the structure of the enzyme, placing some strain on the substrate and further facilitating the reaction.
Cofactors are nonproteins essential for enzyme activity.
Coenzymes are nonprotein organic molecules bound to enzymes near the active site. A cartoonish view of the formation of an enzyme-substrate complex. Image from W.H. Freeman and Sinauer Associates, used by permission. Enzymatic pathways form as a result of the common occurrence of a series of dependent chemical reactions. In one example, the end product depends on the successful completion of five reactions, each mediated by a specific enzyme.