The process of enzyme catalysis of biological processes follows a simple pathway and involves three principal species.
The substrate, which we will represent as S, is the molecule that is to undergo reaction. The enzyme, E, acts as the catalyst, and the product, P, is the result of the reaction.
The substrate, S, attaches to a receptor site on the enzyme, E, where it is held in place as the reaction proceeds. Once reaction is completer, the product, P, is released from the receptor site, along with any remaining portion of the substrate molecule.
The process can be represented as shown below, where S-E represents the substrate, bound to the catalyst. As the product forms, the receptor site on the catalyst is again freed to accept another substrate molecule.
$S+E\to [S-E]\to P+E$
The reaction rate can be investigated either in terms of decreasing concentration of substrate, or increasing appearance of product.
As part of her senior-year STEM project, Athena designs an experiment to study a particular enzyme-catalyzed reaction. Since the product of the reaction is a colored species, she sets up a colorimetric interface to measure the rate of appearance of the colored product, in units of concentration of product over time: $\frac{mol.L^{-1}}{min}$, or simply, $\frac{M}{min}$. The plot of product formation vs time appears below.
By design, Athena's experiment began with a large excess of the substrate, S, relative to the enzyme, E.
Which of the following offers the BEST description of the results of her study?

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