Rights: The University of Waikato Published 20 November 2007 Download

Does cell chemistry differ from "ordinary" chemistry?


Sir Paul Nurse: There is something unusual about the chemistry that goes on in living cells. I’ve put this diagram up there to illustrate what I mean by this, because this isn’t like industrial chemistry where you have major vats carrying out chemical reactions - single chemical reactions.

What you’ve got here is a tiny little object a few, 10-20 micrometres across, and within it are many hundreds, if not thousands, of chemical reactions going on at the same time in this tiny space. Now that can only come about because each of those chemical reactions requires subtly different conditions from one to another. It can only come about if the cell separates this space in the cell, so that there are individual pockets, or micro-environments, for each of the chemical reactions.

For example, what we see is, all these reactions generally take place on enzymes, these proteins I’ve already spoken about. And it’s the surface of the enzyme that isolates and makes a little chemical micro-environment that allows chemical changes to actually take place. And I’ve drawn that here. What we have is a membrane around here keeping a cell separate from the environment. Here we have a simple enzyme made up from a single protein, and a sort of pocket there which keeps an isolated chemical surface. And then we have another one down here made of two proteins, for example, and others which have higher numbers of proteins involved, more complex structures. This is channelling, where a substrate makes a product and that becomes a substrate for the next reaction, and so on.

All of these are examples of little chemical micro-environments, and there are hundreds of them operating in the cell at any one time. And that reflects the complexity that you see in a cell.

But this in itself is not good enough, and it's not good enough because if we leave it like that, we have hundreds of chemical reactions going on seperately from each other. That doesn’t produce the overall functioning of a cell. These reactions have to communicate with each other. For example, what I’d be arguing is is that you can have local regulation and local communication but if this chemical environment here has to be kept separate, for example, from this one here, but has to be co-ordinated from this one here. You have to signal from one to the other. So what we are dealing with is an extraordinarily complicated chemical machine where all the different chemistries are co-ordinated, one with another, to give a functioning whole.