Carnitine is a vitamin like substance whose primary function is to transport fat from the cell into the mitochondria in order to be burned. To be more specific (read... in Bio-Geek terms), carnitine transports long chained fatty acids across the inner mitochondrial membrane and into the mitochondrial matrix. Once in the mitochondrial matrix the fatty acids undergo ß-oxidation. Beta oxidation is the process where fatty acids are tranformed into Acetyl-Co-A which is the entry molecule for the Krebs Cycle or what is also known as the Citric Acid Cycle ot TCA Cycle. The Citric Acid Cycle is the process where cellular respiration (the site where oxygen is ultimately used in breathing animals and where carbon dioxide is created) occurs and energy (or ATP and GTP) is used.