Atp is composed of phosphate groups attached to adenosine, a unit composed of adenine and the sugar ribose.

the binding of the substrate is dictated by the shape of each molecule. side chains on the enzyme interact with the substrate in a specific way, resulting in the making and breaking of bonds.

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.