And a ternary structure is a structure in which the active side of the enzyme is filled with the two substrate molecules A and B. So the defining property of sequential reactions is that all the substrates, the two substrates A and B, have to bind to the active site of the enzyme to form the ternary structure that consists of the enzyme and the two substrates before the catalysis process can actually take place. And we can convert those reactants into the products. Now, we can further subdivide sequential reactions into two types. We have ordered sequential reactions, and we have random sequential reactions. And let's begin by focusing on the ordered sequential reaction.