Aerobic Respiration Section 9:2

Overview Krebs Cycle: In the presence of O2, Pyruvic Acid oxidizes, the reduction of NAD + to NADH, and FAD to FADH, and a small amount of ATP is made. Krebs or the ETC. will only occur if, CO2, H2O and O2 are ALL present.

Aerobic Respiration – Oxygen Present Occurs in the mitochondria of eukaryotes and the cytosol of prokaryotes. Pyruvic acid, from Glycolysis, diffuses in from the cytosol to the mitochondrial matrix. –The space inside the inner membranes

Fig. 7.5a, p. 114 inner compartmentouter compartmentcytoplasm outer mitochondrial membrane inner mitochondri al membrane (see next slide)

Aerobic Respiration – before KC Pyruvic acid joins with coenzyme A (CoA), no carbons, to form acetyl CoA – 2 carbons CO 2 is lost in this process and NAD is reduced to NADH and H +.

Krebs Cycle A biochemical pathway that breaks down acetyl CoA producing CO 2, NADH, FADH, and ATP and Citric acid. 5 steps to the Krebs cycle

Step 1 The 2-carbon acetyl CoA combines with a 4-carbon compound, oxaloacetic acid, to form a 6-carbon molecule, citric acid This step regenerates co- enzyme A

Fig. 7.6, p. 115 oxaloacetate malate citrate isocitrate  -ketogluterate fumarate succinate CoA succinyl–CoA ATP NADH FADH 2 NAD + FAD NAD + CoA H2OH2O H2OH2O H2OH2O ADP + phosphate group (from GTP) KREBS CYCLE PREPARATORY STEPS pyruvate NAD + CoA Acetyl–CoA coenzyme A (CoA) (CO 2 )

Step 2 Citric acid releases a CO 2 and a hydrogen to form a 5-carbon compound NAD + accepts an H + to become NADH and H +.

Fig. 7.6, p. 115 oxaloacetate malate citrate isocitrate  -ketogluterate fumarate succinate CoA succinyl–CoA ATP NADH FADH 2 NAD + FAD NAD + CoA H2OH2O H2OH2O H2OH2O ADP + phosphate group (from GTP) KREBS CYCLE PREPARATORY STEPS pyruvate NAD + CoA Acetyl–CoA coenzyme A (CoA) (CO 2 )

Step 3 The 5-carbon compound releases CO 2 and H + to form a 4-carbon compound. NAD + is reduced again to NADH and One molecules of ATP is made

Fig. 7.6, p. 115 oxaloacetate malate citrate isocitrate  -ketogluterate fumarate succinate CoA succinyl–CoA ATP NADH FADH 2 NAD + FAD NAD + CoA H2OH2O H2OH2O H2OH2O ADP + phosphate group (from GTP) KREBS CYCLE PREPARATORY STEPS pyruvate NAD + CoA Acetyl–CoA coenzyme A (CoA) (CO 2 )

Step 4 The 4-carbon compound releases hydrogen The hydrogen forms with FAD + to form FADH 2. FAD is another electron acceptor.

Fig. 7.6, p. 115 oxaloacetate malate citrate isocitrate  -ketogluterate fumarate succinate CoA succinyl–CoA ATP NADH FADH 2 NAD + FAD NAD + CoA H2OH2O H2OH2O H2OH2O ADP + phosphate group (from GTP) KREBS CYCLE PREPARATORY STEPS pyruvate NAD + CoA Acetyl–CoA coenzyme A (CoA) (CO 2 )

Step 5 The 4-carbon compound releases a hydrogen to REFORM oxaloacetic acid NAD + is reduced again to NADH and H +

Fig. 7.6, p. 115 oxaloacetate malate citrate isocitrate  -ketogluterate fumarate succinate CoA succinyl–CoA ATP NADH FADH 2 NAD + FAD NAD + CoA H2OH2O H2OH2O H2OH2O ADP + phosphate group (from GTP) KREBS CYCLE PREPARATORY STEPS pyruvate NAD + CoA Acetyl–CoA coenzyme A (CoA) (CO 2 )

Glycolysis, produces 2 NADH and 2 pyruvic acid, 2 ATP. One molecule of glucose from glycolysis needs 2 turns of the Krebs to produce: Summary: 10 NADH, 2 FADH, 4 ATP, 4 CO2. The 10 NADH and 2 FADH (both energy molecules) will drive the next stage of cellular respiration in the Electron Transport Chain.

Krebs Cycle conclusion Location – Mitochondrial Matrix (space inside the inner membrane) Function – Produce CO2, ATP, NADH, FADH and Citric Acid. Reactants – Pyruvic Acid,Acetlyl-CoA, Oxaloacitic Acid, NAD, FAD, ADP and C0enzyme A. Products – CO2 NADH, FADH, ATP and Citric acid.

The Electron Transport Chain in Cellular Respiration

Cellular Respiration The process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.

Electron Transport Chain A chemical reaction that uses high energy electrons made in the Krebs cycle to convert ADP into ATP. Aerobic – means with oxygen Anaerobic – means without oxygen

Electron Transport Chain ATP is produced when NADH and FADH 2 release hydrogen atoms, regenerating NAD + and FAD +. This occurs along the lining of the inner membranes of the mitochondria.

Steps of ETC 1. Electrons from the hydrogens atoms of NADH and FADH are passed along a series of molecules, losing energy along the way.

2. This energy pumps protons from the matrix to the other side of the membrane. This creates a concentration gradient across the inner membrane of the mitochondria.

NADH Fig. 7.7a, p. 116 OUTER COMPARTMENT INNER COMPARTMENT

3. This high proton concentration is what drives chemiosmosis ( ATP production) into the inner membrane. ATP synthase is located in the inner membrane. ATP is made as protons move down their concentration gradient in the mitochondria.

Oxygen’s Role Oxygen is the final electron acceptor, accepting electrons from the last molecule in the ETC. This allows ATP to continue to be synthesized. Oxygen also accepts the hydrogen atoms from NADH and FADH. This combination of electron, hydrogens and oxygen forms WATER!!!!! O2 + e- +H- = H2O

NADH ATP ADP + P i Fig. 7.7b, p. 116 INNER COMPARTMENT

Energy Yield Per molecule of glucose, 36 ATP’s are produced. 2 in Glycolysis, and approximately, 4 in Krebs and 30 in ETC. C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy

Fig. 7.5b, p. 114 Krebs Cycle NADH ATP ADP + P i INNER COMPARTMENT OUTER COMPARTMENT acetyl-CoA free oxygen 6 Following its gradients, H + flows back into inner compartment, through ATP synthases. The flow drives ATP formation. 1 Pyruvate from cytoplasm enters inner mitochondrial compartment. 3 NADH and FADH 2 give up electrons and H + to membrane- bound electron transport systems. 2 Krebs cycle and preparatory steps: NAD + and FADH 2 accept electrons and hydrogen stripped from the pyruvate. ATP forms. Carbon dioxide forms. 5 Oxygen accepts electrons, joins with H + to form water. 4 As electrons move through the transport system, H + is pumped to outer compartment.

Krebs Cycle and ETC. Both the Krebs Cycle and the Electron Transport chain can not proceed without the presence of O2 H2O CO2

Conclusion of Electron Transport Chain Location – Lining of the inner membrane of the mitochondria. Function – Produce ATP and water Reactants – NADH, FADH, ADP and O2. Products – NAD, FAD, ATP and Water

Order of processes in Cellular Respiration. 1. Glycolysis 2. Krebs cycle 3. Electron Transport Chain

# of carbon atoms in compounds CO2 – 1PGA - 3 RuBP – 5PGAL - 3 Glucose – 6 Oxaloacitic Acid – 4 Acetyl Co-A – 2 Pyruvic Acid – 3 Citric Acid – 6 Lactic Acid – 3 Ethyl Alcohol – 2 Co-enzyme A - 0