Question

how can you calculate the $k_i$ for a competitive inhibition?
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a) by comparing either the slopes or the y-intersects of lineweaver-burk plots at different inhibitor concentrations
b) by comparing both slopes and y-intercepts of lineweaver-burk plots at different inhibitor concentrations
c) by comparing the y-intersects of lineweaver-burk plots at different inhibitor concentrations
d) by comparing the slopes of lineweaver-burk plots at different inhibitor
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Explanation:

For competitive enzyme inhibition, the Lineweaver-Burk plot's y-intercept (which correlates to $\frac{1}{V_{max}}$) remains unchanged across different inhibitor concentrations, while the slope (which correlates to $\frac{K_m}{V_{max}}$) increases with higher inhibitor levels. To calculate $K_i$, one uses the change in slope between plots with and without inhibitor, as the y-intercept does not shift.

Answer:

d) By comparing the slopes of Lineweaver-Burk plots at different inhibitor concentrations