Cellular Respiration Part III: Krebs Cycle

Electrons carried via NADH Electrons carried via NADH and FADH2 Figure 9.6-3 Electrons carried via NADH Electrons carried via NADH and FADH2 Oxidative phosphorylation: electron transport and chemiosmosis Glycolysis Citric acid cycle Pyruvate oxidation Glucose Pyruvate Acetyl CoA CYTOSOL MITOCHONDRION So far we have explored Glycolysis and the formation of acetyl CoA. Today we will follow the remnant glucose as it is processed through the Krebs cycle. ATP ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Oxidative phosphorylation

Citric Acid Cycle (Krebs Cycle) Krebs Cycle

Curriculum Framework 3. In the Krebs cycle, carbon dioxide is released from organic intermediates, ATP is synthesized from ADP and inorganic phosphate via substrate level phosphorylation, and electrons are captured by coenzymes. 4. Electrons that are extracted in the series of Krebs cycle reactions are carried by NADH and FADH2 to the electron transport chain.

Pyruvate CO2 NAD CoA NADH + H Acetyl CoA CoA CoA Citric acid cycle Figure 9.11 Pyruvate CO2 NAD CoA NADH + H Acetyl CoA CoA CoA Citric acid cycle 2 CO2 Here is an overview of pyruvate oxidation and the citric acid cycle. FADH2 3 NAD FAD 3 NADH + 3 H ADP + P i ATP

Krebs Cycle Occurs in the mitochondrial matrix Releases the remaining carbons from the remnant glucose Transfers the energy to NAD, FAD, and ADP Details worth knowing!

Citric acid cycle Figure 9.12-8 Acetyl CoA Oxaloacetate Malate Citrate CoA-SH NADH + H 1 H2O NAD Oxaloacetate 8 2 Malate Citrate Isocitrate NAD Citric acid cycle NADH 3 7 + H H2O CO2 Fumarate CoA-SH -Ketoglutarate One last NADH formation and the cycle is complete. 4 6 CoA-SH 5 FADH2 CO2 NAD FAD Succinate P i NADH GTP GDP Succinyl CoA + H ADP ATP

Acetyl CoA 1 Oxaloacetate 2 Citrate Isocitrate H2O CoA-SH Figure 9.12a Figure 9.12 A closer look at the citric acid cycle. Oxaloacetate 2 Citrate Isocitrate

3 4 Isocitrate -Ketoglutarate Succinyl CoA NAD NADH + H CO2 CO2 Figure 9.12b Isocitrate NAD NADH 3 + H CO2 CoA-SH -Ketoglutarate 4 Figure 9.12 A closer look at the citric acid cycle. CO2 NAD NADH Succinyl CoA + H

Fumarate 6 5 Succinate Succinyl CoA FADH2 FAD P i GTP GDP ADP ATP Figure 9.12c Fumarate 6 CoA-SH 5 FADH2 FAD Succinate P i Figure 9.12 A closer look at the citric acid cycle. GTP GDP Succinyl CoA ADP ATP

Oxaloacetate 8 Malate 7 Fumarate NADH + H NAD H2O Figure 9.12d Figure 9.12 A closer look at the citric acid cycle. H2O Fumarate

Where does each atom end up? C6H12O6 C = given off as carbon dioxide H = transferred to NAD or FAD O = Given off as carbon dioxide

So what did we get from Krebs? Name the energy related end products of Krebs. By what process is ATP formed? Name the waste products. Where do the events of Krebs occur? Do cells in all kingdoms go through the Krebs cycle? Where are the electrons headed?

So, What Did We Get From Krebs?

Electrons carried via NADH Electrons carried via NADH and FADH2 Figure 9.6-3 Electrons carried via NADH Electrons carried via NADH and FADH2 Oxidative phosphorylation: electron transport and chemiosmosis Glycolysis Citric acid cycle Pyruvate oxidation Glucose Pyruvate Acetyl CoA CYTOSOL MITOCHONDRION Figure 9.6 An overview of cellular respiration. ATP ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Oxidative phosphorylation

Curriculum Framework f. Cellular respiration in eukaryotes involves a series of coordinated enzyme-catalyzed reactions that harvest free energy from simple carbohydrates.