<Li> Pyruvate is taken up by a specific, low Km transporter to bring it into the mitochondrial matrix for oxidation by the pyruvate dehydrogenase complex . </Li> <Li> The phosphate carrier (PiC) mediates the electroneutral exchange (antiport) of phosphate (H PO; P) for OH or symport of phosphate and protons (H) across the inner membrane, and the driving force for moving phosphate ions into the mitochondria is the proton motive force . </Li> <Li> The ATP - ADP translocase (also called adenine nucleotide translocase, ANT) is an antiporter and exchanges ADP and ATP across the inner membrane . The driving force is due to the ATP (− 4) having a more negative charge than the ADP (− 3), and thus it dissipates some of the electrical component of the proton electrochemical gradient . </Li> <P> The outcome of these transport processes using the proton electrochemical gradient is that more than 3 H are needed to make 1 ATP . Obviously this reduces the theoretical efficiency of the whole process and the likely maximum is closer to 28--30 ATP molecules . In practice the efficiency may be even lower because the inner membrane of the mitochondria is slightly leaky to protons . Other factors may also dissipate the proton gradient creating an apparently leaky mitochondria . An uncoupling protein known as thermogenin is expressed in some cell types and is a channel that can transport protons . When this protein is active in the inner membrane it short circuits the coupling between the electron transport chain and ATP synthesis . The potential energy from the proton gradient is not used to make ATP but generates heat . This is particularly important in brown fat thermogenesis of newborn and hibernating mammals . </P>

Where are nutrients broken down to produce atp during the process of aerobic cellular respiration