Table of Contents

• Part I: Using intuition to think about the shape of the graph
• 1: Stalking the wild equation
• 2: What beast are we looking for?
• 3: The outline of the beast
• 4: The middle of the beast
• 5: The whole beast
• Part II: Exploring the M-M equation
• 6: The M-M equation
• 7: Notice the %
• 8: Different values for K_m
• 9: Using (and abusing) K_m
• 10: K_m in the crosshairs
• 11: What's special about K_m?
• 12: Fun with graphs
• 13: Michaelis Menten in a nutshell.
• Part III: Exploring the Lineweaver-Burke plot
• 14: Problem: how to measure K_m and V_max
• 15: Solution: a strange transformation
• 16: Measuring V_max
• 17: Measuring K_m
• Part IV: Using it all
• 18: Virtual experiment, real enzyme
• 19: Two preservatives, new kinetics
• 20: How do these preservatives work?

Notice the %

Here's the equation again:

After staring at this equation some more, something occurs to me. The equation is trying to tell me that the actual rate of product formation (V) can be found by taking the maximum rate and multiplying it by some thing (not sure what yet) that involves substrate concentration:

Since of V_max is the maximum velocity, I would have to guess that the "something" is a number between zero and one. If the "something" was less than zero, and we would have a negative rate of product formation, and no negative numbers appear on the graph. If the "something" was greater than one, then it would be possible for the is one reaction to exceed V_max, which we are to know is impossible. Otherwise we wouldn't call it V_max.

So now, at least we've simplify the problem little. The part of the equation that is still confusing. Is this:

[S] is clearly the concentration of substrate. But what is K_m? Well, K_m can't be either the dependent or the independent variable. What's left? It has to be either a constant or parameter. A constant is a number which always stays the same, such as pi equals 3.1415 etc. A parameter, on the other hand, is a number that takes on different values depending on the conditions.

Actually, there are very few real constants in the world. Maybe just death and taxes. Most other things are parameters. Including K_m. Therefore, K_m could have one value for chocolatase at room temperature, a different value for chocolatase in an ice box, and yet another value for o-diphenol oxidase acting on an apple on your lab bench on a hundred-degree day.