Discussion
For an enzyme that follows Michaelis-Menten kinetics, a competitive inhibitor
Answer: C
A competitive inhibitor increases \(K_{m}\) but does not affect \(V_{max}\).
A competitive inhibitor binds the free enzyme at the active site, competing with the substrate. More substrate is needed to reach half-maximal velocity, so the apparent \(K_{m}\) rises by the factor \((1 + [I]/K_{i})\). At very high substrate concentration, however, the substrate outcompetes the inhibitor completely, so the maximal velocity is unchanged.
On a Lineweaver-Burk plot the lines therefore meet on the y-axis (same \(1/V_{max}\)). Lowering both \(K_{m}\) and \(V_{max}\) is the signature of uncompetitive inhibition; changing \(V_{max}\) at all rules out competitive inhibition, and a decrease in \(K_{m}\) never results from competition with the substrate.
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