Oxidative Phosphorylation and ATP 24.5 ATP Energy from Glucose Chapter 24 Metabolism and Energy Production

2 Chemiosmotic Model In the chemiosmotic model: Complexes I, III, and IV pump protons into the intermembrane space, creating a proton gradient. Protons must pass through ATP synthase to return to the matrix. The flow of protons through ATP synthase, provides the energy for ATP synthesis (oxidative phosphorylation): ADP + P i + Energy ATP

3 Chemiosmotic Model of Electron Transport

4 ATP Synthase In ATP synthase: Protons flow back to the matrix through a channel in the F 0 complex. Proton flow provides the energy that drives ATP synthesis by the F 1 complex.

5 ATP Synthase F 1 Complex In the F 1 complex of ATP synthase: A center subunit (  ) is surrounded by three protein subunits: loose (L), tight (T), and open (O). Energy from the proton flow through F 0 turns the center subunit (  ), which changes the shape (conformation) of the three subunits.

6 ATP Synthesis in F 1 During ATP synthesis: ADP and P i enter the loose L site. The center subunit turns changing the L site to a tight T conformation. ATP is formed in the T site where it remains strongly bound. The center subunit turns changing the T site to an open O site, which releases the ATP.

7 ATP Synthase F 1 Diagram

8 In electron transport, the energy level decrease for electrons: From NADH (Complex I) provides sufficient energy for 3ATPs. NADH + 3ADP + 3P i NAD + + 3ATP From FADH 2 (Complex II) provides sufficient energy for 2ATPs. FADH 2 + 2ADP + 2P i FAD + 2ATP Electron Transport and ATP

9 ATP from Electron Transport

10 Regulation of Electron Transport In the electron transport system: Low levels of ADP, P i, oxygen, and NADH decrease electron transport activity. High levels of ADP activate electron transport.

11 ATP Energy from Glucose The complete oxidation of glucose yields 6CO 2, 6H 2 O, and 36 ATP.

12 In glycolysis: Glucose forms 2 pyruvate, 2 ATP and 2NADH. NADH produced in the cytoplasm cannot enter the mitochondria. A shuttle compound (glycerol-3-phosphate) moves hydrogen and electrons into the mitochondria to FAD, which forms FADH 2. Each FADH 2 provides 2 ATP. Glucose 2 pyruvate + 6 ATP ATP from Glycolysis

13 ATP from Glycolysis Reaction Pathway ATP for One Glucose ATP from Glycolysis Activation of glucose-2 ATP Oxidation of 2 NADH (as FADH 2 ) 4 ATP Direct ADP phosphorylation (two triose) 4 ATP Summary: C 6 H 12 O 6 2 pyruvate + 2H 2 O + 6 ATP glucose

14 ATP from Two Pyruvate Under aerobic conditions: 2 pyruvate are oxidized to 2 acetyl CoA and 2 NADH. 2 NADH enter electron transport to provide 6 ATP. Summary: 2 Pyruvate 2 Acetyl CoA + 6 ATP

15 One turn of the citric acid cycle provides: 3 NADH x 3 ATP =9 ATP 1 FADH 2 x 2 ATP =2 ATP 1 GTP x 1 ATP = 1 ATP Total = 12 ATP Acetyl CoA 2 CO ATP Because glucose provides two acetyl CoA, two turns of the citric acid cycle produce 24 ATP. 2 Acetyl CoA 4 CO ATP ATP from Citric Acid Cycle

16 ATP from Citric Acid Cycle Reaction Pathway ATP for One Glucose ATP from Citric Acid Cycle Oxidation of 2 isocitrate (2NADH) 6 ATP Oxidation of 2  -ketoglutarate (2NADH)6 ATP 2 Direct substrate phosphorylations (2GTP) 2 ATP Oxidation of 2 succinate (2FADH 2 ) 4 ATP Oxidation of 2 malate (2NADH) 6 ATP Summary: 2Acetyl CoA 4CO 2 + 2H 2 O + 24 ATP

17 One glucose molecule undergoing complete oxidation provides: From glycolysis 6 ATP From 2 Pyruvate 6 ATP From 2 Acetyl CoA 24 ATP Overall ATP Production for One Glucose: C 2 H 12 O 6 + 6O ADP + 36P i Glucose 6CO 2 + 6H 2 O + 36ATP ATP from Glucose