Plasmodium falciparum gametocytes primarily use glucose to fuel the tricarboxylic acid (TCA) cycle. (A,B)Trophozoite-infected red blood cell (RBCs) (A) and gametocytes (G), and uninfected RBCs (R) were cultivated in medium containing 8 mmol/l13C-U-glucose or 13C-U-glutamine. (A) Uptake of 13C-glucose and secretion of 13C-lactate and 13C-acetate was monitored by 13C nuclear magnetic resonance imaging (13C NMR) analysis of the medium over 24 hours, and compared with the initial medium (t0). No changes were seen in glucose, lactate, or acetate levels in medium lacking RBCs (M). (B) Gametocytes were cultured in the presence of 13C-glucose or 13C-glutamine for the indicated times, and 13C-enrichment in key metabolites determined by gas chromatography–mass spectrometry (GC-MS). Changes in the major isotopomer of each metabolite over the first 5 hours are shown. Results are the mean of three biological replicates.