In enzyme inhibition studies, if the uninhibited rate is v0 and the inhibited rate is vi, how is the degree of inhibition defined?

Introduction / Context:
Quantifying inhibitor impact helps compare compounds and conditions. A simple normalized metric—degree of inhibition—expresses fractional activity loss relative to the uninhibited control.

Given Data / Assumptions:

• Two measured rates: v0 (no inhibitor) and vi (with inhibitor).
• Same assay conditions except for inhibitor presence.

Concept / Approach:
Fractional loss relative to the control is computed by subtracting the inhibited rate from the control rate and normalizing by the control: (v0 - vi)/v0. This yields values from 0 (no inhibition) to 1 (complete inhibition).

Step-by-Step Solution:

Verification / Alternative check:
Define residual activity as vi/v0; then degree of inhibition = 1 - residual activity = 1 - (vi/v0), which simplifies to (v0 - vi)/v0.

Why Other Options Are Wrong:

• (v0 + vi)/v0 inflates the value; not a loss metric.
• (v0 * vi)/v0 reduces to vi; not normalized to loss.
• (v0 - vi)/vi diverges as vi → 0 and is not bounded by 1.
• vi/v0 is residual activity, not degree of inhibition.

Common Pitfalls:
Mixing up residual activity with inhibition, or failing to normalize to the correct baseline.

Final Answer:
(v0 - vi) / v0.