Lecture_N - ontrol of ATP Synthesis Antioxidants •...

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Unformatted text preview: ontrol of ATP Synthesis. Antioxidants • Coordinated control of oxidative metabolism • The mechanism of ATP synthesis • Advantages and disadvantages of the aerobic metabolism • Cytochrome P450 • Oxygen deprivation in the heart attack and stroke Learning Objectives • Reactive oxygen species and antioxidants • Uncoupling Electron Transport and Oxidative Phosphorylation ATP Synthase, a Molecular Motor • F forms a wheel. F 1 consists of a rod with one end fixed to the wheel's hub. The other end of the rod is embraced by a bundle of six α / β subunits. Protons pass via the mitochondrial membrane back to the matrix forcing the rod to rotate within the stationary bundle. The rotation provides a mechanical energy necessary to catalyze the endergonic combining of ADP and P i . Fig. 17-25 olecular Bearing Figure 17-22. • Contacting surfaces of the rod and the wheel lack polar and ionogenic groups and contain predominantly hydrophobic residues that lubricate the bearing. • One proton passing the F channel swings F 1 by 120 . The synthesis of one ATP molecule from ADP and P i requires three protons to make a 360 turn of the rod. • The 1997 Nobel prize was awarded to Paul Boyer and John Walker for their discovery of mechanism of ATP synthesis and to Jens Skou for his discovery of Na + /K + ATPase. The Mechanism of ATP synthesis • The three identical α / β interfaces can adopt three different conformations. - Open conformation O does not bind ligands.- Catalytically inactive conformation L binds ligands loosely.- Catalytically active conformation T binds ligands tightly. Fig. 17-26 The Mechanism of ATP synthesis • Three-step ATP synthesis:- ADP and P i bind to site L;- Conformational transitions: L → T, T → O, and O → L;- ATP is synthesized at site T; ATP is released from site O. • The energy for the conformational changes within the α 3 β 3 assembly is obtained from the asymmetric rod rotation. Uncoupling Electron Transport and Oxidative Phosphorylation • Electron transport and oxidative phosphorylation are tightly coupled. • Electron transport and oxidative phosphorylation are tightly coupled....
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This note was uploaded on 01/27/2011 for the course BIOCH 2EE3 taught by Professor Zhorovb during the Spring '10 term at McMaster University.

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Lecture_N - ontrol of ATP Synthesis Antioxidants •...

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