Studies from our laboratories over recent years have uncovered the existence, and established the properties of a variety of mitochondrial transporters. The properties of these transporters throw light on a variety of biochemical phenomena that were previously poorly understood. In particular the role of mitochondrial transport in energy metabolism has been investigated under a variety of physio-pathological conditions. Consistently we describe the procedure to investigate mitochondrial traffic in isolated mitochondria as a model system for students to learn. Here we report some observations that contribute to novel knowledge of the role of mitochondria in glycolysis, urea and purine nucleotide cycle, and nitrogen metabolism with particular reference to the malate/oxaloacetate shuttle and fumarate, glutamine, and lactate metabolism.