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Published byMolly Francis Modified over 9 years ago
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KREB’S CYCLE
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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
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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
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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
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1.Acetyl-CoA (2 original carbons) reacts with oxaloacetate to produce citrate (6 carbons) Two citrate are produced per glucose KREB’S CYCLE
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2.Citrate (6 carbons) is converted to Isocitrate (6 carbons) Two isocitrate are produced per glucose KREB’S CYCLE
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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
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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
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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
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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
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7.Fumarate (4 carbons) is converted to Malate (4 carbons) -Using the addition of water Two malate are produced per glucose KREB’S CYCLE
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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
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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
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