I'm not sure if this answers your question: If an algae produces molecule A, one can determine its structure and (in theory) synthesize it in a lab. Both will

I'm not sure if this answers your question: If an algae produces molecule A, one can determine its structure and (in theory) synthesize it in a lab. Both will be structurally identical. Of course, if the chemist wants to add X or Y moieties to the original algal molecule, he can. One could also determine the source of a certain molecule (bio vs. lab) by looking at the different isotopes in each molecule. (In theory because some syntheses are practically extremely difficult.)