Why is it important to get fatty acids into the mitochondria

The mitochondria, in ancient times, used to be a species of it's own. Until one day a unicellular organisms gobbled up a mitochondria and digested it. The mitochondria continued doing it's mechanical functions. (like protein synthesis etc..) Therefore, mitochondria is a living being on it's own sense and hence needs the essential nutrients (like all living beings do) to continue doing it's mechanical functions.