Toxoplasma gondii and all other parasites of the phylum Apicomplexa reside and replicate exclusively within eukaryotic cells. It suggests that these parasites depend on the metabolism of their hosts and that they have evolved metabolic pathways reflecting their intracellular lifestyle. In addition, these parasites may display specific or alternate metabolism as documented by the recent discovery of novel metabolic pathways in the remnant and vestigial plastid (apicoplast) found in many apicomplexan parasites. While targeting unique parasite pathways is an attractive strategy, in practice the procurement of enough pure parasites for biochemical study or purification of parasite components such as enzymes is extremely difficult. Biochemical and metabolic studies of T. gondii have also been difficult to execute because of continual problems with contamination of parasite preparations with host-cell components.