Understand xenobiotic-induced mitochondrial impairment. The Glucose / Galactose assay (Glu/Gal) uses the human hepatocellular carcinoma derived cell line, HepG2 (ATCC HB-8065).nnThe HepG2 cell line has a unique property that allow the cells to produce ATP by either oxidative phosphorylation (mitochondrial dependent) or glycolysis (using the glucose present in media). Replacing the glucose (25mM) with galactose (10mM) in the media limits the cells ability to produce ATP by glycolysis. This means the cells can only produce ATP in the mitochondria via oxidative phosphorylation, effectively circumventing the Crabtree Effect. When comparing the glucose based media to the galactose based media it becomes possible to identify mitochondrial specific toxins by measuring the difference in IC50 values between the two.