using the picture how ATP synthesis is coupled to ..
When two reactions are coupled, ..
ATP is formed in the aqueous space bounded by the mitochondrial inner membrane. This space is known as the matrix (see Fig. 7). Most of the ATP generated within mitochondria is exported to the cytoplasm where it is used to drive energy-dependent reactions. The ADP and Pi formed in the cytoplasm must then be taken up by the mitochondria. The inner membrane contains specific proteins that mediate the export of ATP and the import of ADP and Pi. One transporter catalyzes counterexchange transport of ATP out of the matrix with ADP in the cytoplasm into the matrix (Fig. 8). At physiological pH, ATP bears four negative charges, and ADP, three. Thus, the one-to-one exchange transport of ATP with ADP creates a membrane potential that is opposite in sign of that created by electron-transport-driven proton translocation. ATP/ADP transport costs energy and the direction of transport is poised by the proton membrane potential. In addition, phosphate uptake into mitochondria is coupled to the electrochemical proton potential. The phosphate translocator (see Fig. 8) catalyzes the counterexchange transport of H2PO4— and hydroxide anion (OH-). The outward movement of OH-causes acidification of the matrix, whereas the direction of proton transport driven by electron transport is out of the mitochondrial matrix and results in an increase in the pH of the matrix.
Microbiology Ch. 5 Flashcards | Quizlet
Electron transport from NADH and FADH2 to oxygen provides the energy for the generation of the electrochemical potential of the proton. The flow of protons down this potential is exergonic and is the immediate source of energy for ATP synthesis. The proton-linked synthesis of ATP is catalyzed by a complex enzyme called ATP syn-thase. Remarkably similar enzymes are located in the coupling membranes of bacteria, mitochondria, and chloro-plasts, the intracellular sites of photosynthesis in higher plants. Even though the reaction that they catalyze seems relatively straightforward (see Fig. 2), the ATP synthases contain a minimum of 8 different proteins and a total of about 20 polypeptide chains.