Today in biology we learnt about the mechanisms of positive and negative feedback loops in regulating transcription. In particular, we learnt about tryptophan (trp) operons. The trp operon uses negative feedback and basically encodes the enzyme for the biosynthesis of tryptophan. This doesn’t happen if you already have tryptophan, which can happen two ways: either your body makes them or you eat something that has it. One source of trp is… chocolate! Apparently trp helps in releasing serotonin which is (very) basically the happy chemical. So high trp means more serotonin which means awesome happy fun times.
However, trp is a co-repressor. It helps to repress the enzyme that’s actually making trp in your body. So, there’s an enzyme or gene or something that makes trp, but when the trp is made, it goes back to this enzyme, which has a repressor on it and the trp binds to the repressor, therefore deactivating it! And so your body stops making trp.
Basically, you get happy because of seratonin because of trp, but then your body’s like “woop! too much happy! better stop making happy!” and then shuts down the trp factory which shuts down the serotonin factory. (There is probably another gene or protein that aids in the release of serotonin from elsewhere, but we haven’t learnt about it so it doesn’t exist yet). So if your body’s stopped making trp then I guess the only way to be more happy is to eat more chocolate!