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[miyuru]

Kd = 1/Ka

But the units for both remain the same right?

For example if Ka for a reaction is measured in 1/M, the dissociation constant would also be in 1/M, not M...I think.

Just curious! (Exam tomorrow)

 

[videogamer]

Kd = 1/Ka

But the units for both remain the same right?

For example if Ka for a reaction is measured in 1/M, the dissociation constant would also be in 1/M, not M...I think.

Just curious! (Exam tomorrow)

Ehhh I'll try to stab at it.

If Kd=1/Ka and Ka=1/M, then the units would be Kd=1/[1/M]=M. So yeah, Kd would then be M, not 1/M. The dimensional analysis wouldn't make sense otherwise.

Sorry for my old gchem knowledge, but I wonder if you are really talking about equilibria (specifically acid-base), not kinetics. Are you sure the "K" is capitalized?

 

[miyuru]

Hm yeah it's capitalised. For example:

P + DNA <-> P-DNA
(P = protein)

Ka would equal: [P-DNA]/[P][DNA] when looking at the forward reaction.

Looking at it through dimensional analysis is always a good way to break things down though, I'm going to trust you on this one!

 

[WHOAguitarninja]

I was gonna say the same thing. I'm not exactly sure what you're talking about, but in no case that I can think of would you have a situation in which M=1/M unless M were a unitless 1, in which case it would be pretty pointless and could just be treated as a constant.

 

[videogamer]

Hm yeah it's capitalised.

For example:

P + DNA <-> P-DNA
(P = protein)

Ka would equal: [P-DNA]^1/([P]^1[DNA]^1) when looking at the forward reaction.

Yeah, it's probably equlibria then. AFAIK/BTW, Ka is reserved for acids. You can use plain Kc for the foward reaction. K' can be the reverse. It actually makes sense if you figure out the units for each reaction... the stoichiometry changes with reactions. However, I remember not even bothering to use units for K and just treating it as an unitless quantity.

In your notation, does Kd denote the reverse reaction away from the protein-DNA complex?