Figure 1.

The figure shows the basic structural components of the ETC complexes (I, II, III, IV, and V) the sites of proton pumping after electron transfer from complex I and complex II during mitochondria substrate oxidation, that leads to the generation of ATP. Fatty acid oxidation and Krebs cycle generate NADH and FADH₂ needed to energize mitochondria and establish the mitochondrial membrane potential (ΔΨ_m; −180 to −200 mV). The ΔΨ_m can be modulated be uncoupling proteins (UCP). Phosphate is imported and exported through the adenine nucleotide translocase (ANT) and this is one way to regulate matrix phosphate levels. Substrate uptake is mediated through mitochondrial inner membrane (IMM) proteins [e.g., carnitine palmitoyl transferase (CPT) and pyruvate dehydrogenase (PDH)]. Ca²⁺, which may modulate mitochondrial respiration is taken up via the calcium uniporter (CaU). Other components of the IMM include the putative transporters/exchangers. These include the Na⁺/H⁺ exchanger (NHE), the K⁺/H⁺ exchanger (KHE) and the Na⁺/Ca²⁺ exchanger (NCE), some of which have been characterized. The putative Ca²⁺/H⁺ exchanger (the so-called Na independent Ca exchanger or NICE; not shown) is considered a likely regulator of ion flux dynamics.