Cellular Respiration Part IV: Oxidative Phosphorylation

Curriculum Framework 2A2 Organisms capture and store free energy for use in biological processes. g. The electron transport chain captures free energy from electrons in a series of coupled reactions that establish an electrochemical gradient across membranes. 2

Figure Electrons carried via NADH Electrons carried via NADH and FADH 2 Citric acid cycle Pyruvate oxidation Acetyl CoA Glycolysis GlucosePyruvate Oxidative phosphorylation: electron transport and chemiosmosis CYTOSOL MITOCHONDRION ATP Substrate-level phosphorylation Oxidative phosphorylation

Oxidative Phosphorylation: Electron Transport and Chemiosmosis 2A2g2. In cellular respiration, electrons delivered by NADH and FADH 2 are passed to a series of electron acceptors as they move toward the terminal electron acceptor, oxygen. Curriculum Framework

t and Chemiosmosis 2A2g3. The passage of electrons is accompanied by the formation of a proton gradient across the inner mitochondrial membrane or the thylakoid membrane of chloroplasts, with the membrane separating a region of high proton concentration from a region of low proton concentration. In prokaryotes, the passage of electrons is accompanied by the outward movement of protons across the plasma membrane. Curriculum Framework

Inner mitochondrial membrane Outer mitochondrial membrane Electron transport chain Electron carrier (NADH) Electrons

OxygenElectrons Hydrogen ions

Water

Hydrogen ions Inner mitochondrial membrane Area of high hydrogen ion concentration ATP synthaseATP

Inner mitochondrial membrane Outer mitochondrial membrane

Chemiosmosis: The Energy-Coupling Mechanism Electron transfer in the electron transport chain causes proteins to pump H + from the mitochondrial matrix to the intermembrane space H + then moves back across the membrane, passing through the enzyme, ATP synthase ATP synthase uses the exergonic flow of H + to drive phosphorylation of ATP This is an example of chemiosmosis, the use of energy in a H + gradient to drive cellular work

Figure 9.14 INTERMEMBRANE SPACE Rotor Stator HH Internal rod Catalytic knob ADP + P i ATP MITOCHONDRIAL MATRIX

Figure 9.15 Protein complex of electron carriers (carrying electrons from food) Electron transport chain Oxidative phosphorylation Chemiosmosis ATP synth- ase I II III IV Q Cyt c FAD FADH 2 NADH ADP  P i NAD  HH 2 H  + 1 / 2 O 2 HH HH HH 21 HH H2OH2O ATP

The energy stored in a H + gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis The H + gradient is responsible for establishing a proton-motive force, emphasizing its capacity to do work

Mitochondrial Membrane Name and describe three structural features that make the mitochondrial membrane effective at the process of energy transfer. 15

ATP Production by Cellular Respiration Arrange these in order of energy transfer through chemiosmosis: electron transport chain Glucose proton-motive force NADH ATP

Figure 9.16 Electron shuttles span membrane MITOCHONDRION 2 NADH 6 NADH 2 FADH 2 or  2 ATP  about 26 or 28 ATP Glycolysis Glucose 2 Pyruvate Pyruvate oxidation 2 Acetyl CoA Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis CYTOSOL Maximum per glucose: About 30 or 32 ATP