Michaelis-Menten & Henderson–Hasselbalch Equations

[Veronica]

Hi guys

 

 

In my studies I've had great difficulty understanding these two equations; I'm not mathematically minded, and however much I read over our notes or ask lecturers for help, its not clicking.

 

If there is a kind and clever person on here who's willing to talk me through these equations with examples I'll be so grateful!

 

 

Thanks a lot

[CharonY]

It is not really a mathematical issue but rather these equations describe chemical properties. The first is a model for enzymatic reaction, i.e. a simplification in order to estimate simple enzyme kinetics, whereas with the HH is for description of an equilibrium reaction useful for the estimation of pH based on known pka values.

 

One does not really need to know mathematics (except very low level) in order to understand the equation and it is potentially distracting for some people to think of it that way. Rather just look at the involved the parameters. For instance, in HH you have the pka, as well the concentrations of the undissociated weak acid and the conjugate base. Looking at the equation it is clear that you have one constant for your system (pka) and then you just need to know the respective concentrations to calculate pH. Or if you know the pH you just need one concentration to solve for the other. It can also be used to experimentally determine pka, if unknown, of course.

 

In a similar way, MM is a way to relate enzyme kinetics (reaction rates) to substrate levels.

 

If things do not click it is advisable to figure out how far you understand those and start asking questions from there. E.g. is it how these equations were derived, or how these equations behave, how they are used, etc. As mathematically it does not go much about simple algebra.

[BabcockHall]

There are a number of mistakes that students typically make with the Michaelis-Menten equation. One of them is to misunderstand K_m, the Michaelis constant. This is concentration of substrate needed to make the velocity of the enzyme equal to half the maximum velocity, V_max. It may or may not be a thermodynamic dissociation constant. Typically one measures the velocity v of an enzyme at multiple substrate concentrations . From these data pairs, one uses a fitting procedure to obtain V_max and K_m. V_max is the horizontal asymptote of a graph of v versus .

[Veronica]

Thanks a lot for your replies guys In terms of me seeing them both as too mathematical I had to put it down to that through plain ignorance as I didn't understand why I've had such difficulty understanding them both, though I realise they aren't complicated. I will go over what you've both said again with some books and see where I get.

 

I appreciate it!