Final answer:
Enzymes sensitive to changes in pH can be graphed using a sigmoid curve (D) for regulatory enzymes and a hyperbolic curve for non-regulatory enzymes.
Step-by-step explanation:
The graphs representing enzymes sensitive to changes in pH include a sigmoid curve. The shape of the graph depends on whether the enzyme is regulatory or non-regulatory. Regulatory enzymes give a sigmoid curve, while non-regulatory enzymes give a hyperbolic curve.
The question at hand is effectively asking about the pH-activity profile of enzymes. These profiles demonstrate the optimal pH at which an enzyme operates and will typically have a peak where enzyme activity is highest. Away from this optimal pH, the activity decreases, leading to a curve that is typically parabolic in nature. However, if an enzyme is regulated and exhibits cooperative binding, the resulting graph may resemble a sigmoid curve due to the enzymes' more complex interaction with substrates and effectors.
The correct answer would be option sigmoid curve (D).