rypanosome cells are small and heterotrophic; they share common characteristics with other members of the phylum Euglenozoa, particularly the stiffening paraxial rod in the flagellum, and characteristics common to the order Kinetoplastida, specifically a large clump of DNA located at one end of the unusually long mitochondrion known as the kinetoplast. Trypanosoma's cell structure plays a vital role in allowing the cell to morph into three forms (trypomastigote, epimastigote, and amastigote) during its lifecycle, depending on where the cell is located in the host's anatomy. The location of the kinetoplast in relation to the nucleus and the flagellum emergence dictate in which stage the trypanosome cell is found. Key sources of the cell's energy, for example acid calcisomes and reservosomes, continue to intrigue scientists. Drug studies that have been performed in order to curb the parasite's energy have yielded information regarding energy-producing glycosomal enzymes, purine and sterol byosynthetic pathways. Trypanosoma uses several methods in order to penetrate the host's cell: active penetration, active induction of receptor-mediated phagocytosis, and opsonin-mediated phagocytosis. The cell's unique structure allows the trypanosome to invade the host cell usually with little or no difficulty, resulting eventually in cell rupture, release of trypomastigotes, and their subsequent multiplication. Trypanosoma cruzi cells differ from their African relatives (Trypanosoma brucei) in that no replication occurs in the bloodstream; rather, the cells are only able to replicate after another cell has been penetrated.