Acetyl-CoA (2C) combines with oxaloacetate (4C) to form citrate (citric acid) (6C)
Loss of CO 2 and electrons occur
Citrate is cycled back to OAA (oxaloacetate)
NAD+ & FAD pick up e- & H+
ATP’s are formed
Glucose is completely oxidized in the end
Oxygen must be present, but not part of the reactions
Krebs Cycle oxaloacetate malate citrate isocitrate -ketogluterate fumarate succinate CoA succinyl–CoA ATP NADH NADH NADH NADH FADH 2 NAD + NAD + FAD NAD + CoA CoA H 2 O H 2 O H 2 O ADP + phosphate group (from GTP) pyruvate NAD + CoA Acetyl–CoA coenzyme A (CoA) (CO 2 )
Must cycle twice to use up the 2 acetyl CoA produced in the mitochondrial matrix.
Mode of ATP Synthesis Substrate Phosphorylation Enzyme transfers a phosphate group from a substrate to ADP Oxidative Phosphorylation Enzymes result in the transfer of electrons to O 2 . This transfer of energy is used to phosphorylate ADP with free P i .
Krebs Cycle NADH NADH NADH ATP ATP ATP ATP ADP + P i INNER COMPARTMENT OUTER COMPARTMENT acetyl-CoA free oxygen 6 H + flows back into inner compartment, through ATP synthases. Flow drives ATP formation. 1 Pyruvate from cytoplasm enters inner mitochondrial compartment. 3 NADH and FADH 2 give up electrons and H + to electron transfer chains. 2 Krebs cycle and preparatory steps: NAD + and FADH 2 accept electrons and hydrogen. ATP forms. Carbon dioxide forms. 5 Oxygen accepts electrons, joins with H + to form water. 4 As electrons move through the transfer chains, H + is pumped to outer compartment.