1. KREB’S CYCLE

2. Discovered by Hans Adolf Krebs who won the nobel prize in 1953 Occurs in the mitochondrial matrix A cyclical metabolic pathway with 8 steps which begins with acetyl-CoA and and ends with oxaloacetate - Two acetyl-CoA molecules enter for every glucose molecule consumed KREB’S CYCLE

3. Each molecule of acetyl-CoA has two original carbon atoms from the starting glucose These carbons are released in Kreb’s from as carbon dioxide -The original glucose molecule is completely consumed All that remains from the original glucose molecule is most of it’s energy stored in the form of ATP and electron carriers -4 ATP: 2 glycolysis, 2 kreb’s -10 NADH: 2 glycolysis, 2 pyruvate oxidation, 6 kreb’s -2 FADH 2 : kreb’s KREB’S CYCLE

6. Overall Equation for Kreb’s cycle: OAA + Acetyl-CoA + ADP + Pi + 3NAD+ + FAD  CoA + ATP + 3 NADH + 3H+ + FADH 2 + 2 CO 2 + OAA KREB’S CYCLE

7. 1.Acetyl-CoA (2 original carbons) reacts with oxaloacetate to produce citrate (6 carbons) Two citrate are produced per glucose KREB’S CYCLE

8. 2.Citrate (6 carbons) is converted to Isocitrate (6 carbons) Two isocitrate are produced per glucose KREB’S CYCLE

9. 3.Isocitrate (6 carbons) is converted to α-ketoglutarate (5 carbons) -Carbon dioxide is given off - NAD+ is reduced to NADH *** The oxidation of CO 2 is coupled to the reduction of NAD+ Two α-ketoglutarate, two carbon dioxide and two NADH are produced per glucose KREB’S CYCLE

10. 4. α-ketoglutarate (5 carbons) is converted to Succinyl-CoA (4 carbons) -Carbon dioxide is given off -NAD+ is reduced to NADH *** The oxidation of CO 2 is coupled to the reduction of NAD+ Two succinyl-CoA, two carbon dioxide and two NADH are produced per glucose KREB’S CYCLE

11. 5.Succinyl Co-A (4 carbons) is converted to Succinate (4 carbons) -ATP is generated by substrate level phosphorylation ** Phosphate replaces CoA, Phosphate is then added to GTP, Phosphate is then transferred to ADP to form ATP Two succinate and two ATP are produced per glucose KREB’S CYCLE

12. 6.Succinate (4 carbons) is converted to Fumarate (4 carbons), oxidation reaction -FAD is reduced to FADH 2 Two fumarate and two FADH 2 are produced per glucose KREB’S CYCLE

13. 7.Fumarate (4 carbons) is converted to Malate (4 carbons) -Using the addition of water Two malate are produced per glucose KREB’S CYCLE

14. 8. Malate (4 carbons) is converted to oxaloacetate (4 carbons,), oxidation reaction -NAD+ is reduced to NADH Two oxaloacetate and two NADH are produced per glucose KREB’S CYCLE

15. Recall: -4 ATP: 2 glycolysis, 2 kreb’s -10 NADH: 2 glycolysis, 2 pyruvate oxidation, 6 kreb’s -2 FADH 2 : kreb’s This is not enough!!! KREB’S CYCLE