Electron transport in the mitochondria.

(A) Electron transport chain. The conversion of glucose to energy in the Krebs cycle requires the reduction of NAD+ to NADH. The reoxidization of NADH occurs through the electron transport chain in the inner mitochondrial membrane. The reaction can be summarized as NADH + H⁺ + 1/2O₂ → NAD⁺ + H₂0. (B) ATP and H⁺flux across the mitochondrial membranes. The reoxidization of NADH to NAD+ in the electron transport chain produces H₂0 and releases energy. This energy is used to drive the production of ATP in the mitochondrial matrix. The adenine nucleotide transporter (Ant) controls the flux of ADP and ATP across the inner mitochondrial membrane. The voltage dependent anion channel (VDAC) regulates the flux of ATP across the outer mitochondrial membrane. Damage to VDAC or ANT can induce cytochrome c–release and initiate the mitochondrial-mediated pathway of apoptosis. Damage to ANT is also accompanied by physical mitochondrial swelling and loss of ΔΨ_M.