And what Thiamine Pyrophosphate actually does is it helps carry out this particular reaction. It acts as a nucleophile, as we'll see in just a moment. So let's begin with this diagram here. So this is the Thymine pyrophosphate, and it is actually attached onto the enzyme. Now, what happens in step one is this transforms from a poor nuclear file to a good nuclear file. And what happens is we have an ionization reaction taking place in which this hydrogen ion basically departs and it leaves a full negative charge on this carbon.