An energy source, the ATP, it needs a carbon source, the bicarbonate, and it also requires a biotin molecule. Now, this is step number one. In step number two, we basically want to take this D methyl melanyl coenzyme A and transform it into the l isomer form. So we want to transform the Dmethylmel coenzyme into the l methylmelanyl coenzyme A. Why? Well, because the enzyme in the last third step of this process, it uses, it only uses the l isomer and not the deisomer.