Answer:
We can plot our results to help us easily identify the factors that can change enzyme activity. There is is a clear link here between the practical and theoretical elements of biology as the impact of concentration (of enzyme and substrate), inhibition, temperature and pH all have characteristic effects on the rate of reaction plot
By plotting the amount of product against time, you should create a curve that looks a little bit like the one pictured. This plot is useful as it allows you to calculate the initial rate of reaction. The initial rate of reaction is the gradient of the straight line portion of the plot, shown by the dotted red line. The initial rate of reaction is when concentrations of enzyme and substrate are known, so this allows fair comparison if you then change initial concentrations of enzymes or substrate.
Once you have multiple reaction rates at different substrate or enzyme concentrations, it is then possible to take this one step further and plot reaction rate against substrate concentration, enzyme concentration, temperature or pH. Plotting reaction rate against substrate concentration typically gives a curve that is similar in shape to the product/time plot. It is, however, a different curve and can tell you different things. Most importantly the Maximal Velocity (Vmax), which is when the enzyme is saturated with substrate and the rate of reaction is highest, and the Michaelis-Mensten constant (Km), which is a measure of the enzyme's efficiency. Note that it is possible in some reactions for the reaction rate to drop once Vmax has been reached, as excess substrate can act as an inhibitor. A plot of reaction rate against enzyme concentration will usually result in a straight line, as typically the volumes of enzyme used are much lower than the volume of substrate; in other words it is similar to the straight line portion of the reaction rate/substrate plot. Eventually this plot will level off in a similar way to the reaction rate/substrate plot, although this is unlikely to be observed in classroom experiments! Reaction rate/pH plots should produce a classic bell curve, with the optimum pH at the peak of the curve, and reaction rate/temperature plots should show an increasing rate of reaction with temperature until an optimum is reached (often between 45 and 55 degrees Celsius), after that the reaction rate drops off quickly as the enzymes become denatured.
Different enzyme inhibitors will also change reaction rate/substrate curves in different ways. A competitive inhibitor (for example, cyanide) competes with the substrate for the active site of the enzyme, reducing the rate of reaction at lower substrate concentrations. Given a high enough concentration of substrate the inhibitor can be overcome, so the same Vmax as the reaction without inhibition can be reached although the Km will be changed. Noncompetitive inhibitors (such as penicillin) do not use the active site of the enzyme, perhaps binding in another place and changing the conformational shape (an allosteric inhibitor). Increasing substrate concentration should still increase the reaction rate, but because enzymes can be inhibited regardless of how saturated their active sites are, both the Vmax and the Km will be changed.
Step-by-step explanation: