Final answer:
In competitive inhibition, the maximum reaction rate (Vmax) stays the same, but the enzyme's affinity for the substrate decreases, causing an increase in the Michaelis constant (KM). This happens because the inhibitor competes with the substrate for the active site but can be outcompeted by increasing substrate concentration. Option 5 is correct answer.
Step-by-step explanation:
The effect of a competitive inhibitor on an enzyme-mediated reaction is a topic that sits firmly within the realm of Biology, specifically within enzymology, a branch concerned with the study of enzymes.
In the case of competitive inhibition, the inhibitor competes with the substrate for the enzyme's active site. This type of inhibitor has a molecular structure similar to that of the substrate, which allows it to bind reversibly to the same site on the enzyme that the substrate would normally occupy.
Due to the nature of competitive inhibition, the maximum velocity (Vmax) of the reaction remains unchanged because the inhibitor's effect can be overcome by increasing the concentration of the substrate, essentially outcompeting the inhibitor. However, it does affect the enzyme's affinity for the substrate, represented by an increased Michaelis constant (KM). As more substrate is needed to reach half of the Vmax, the KM is higher in the presence of a competitive inhibitor.
Therefore, the correct option in relation to the question regarding the effect of competitive inhibition on an enzyme-mediated reaction is 5) Vmax stays the same, KM increases.