Page 200 - The Manga Guide to Biochemistry

Reaction rate (pmol/hour) Why do we take reciprocals?

Yes, why do we take reciprocals? It’s a mystery, isn’t it? Heh heh heh...

Don’t look at me! Math isn’t really my thing.

Don’t worry. We’ll solve the mystery together. ♪
First, focus on Vmax. In the following graph, you can see that as the substrate

concentration values get larger, the reaction rate measurements approach Vmax.

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Substrate concentration (µM)

You’re right. As the substrate concentration increases, the reaction rate approaches
its limit, Vmax, which is the maximum rate.

If we keep taking measurements like this, we’ll be able to figure out Vmax,
1/2 Vmax, and Km, right?

In theory, that’s true—we could just take a bunch of measurements, and eventually
we’d approach Vmax, but in practice, it’s a bit more difficult than that.

Huh? But why?

186 Chapter 4