energy metabolism (CAC, ETC, Oxidation Phosphorylation)

Krebs Cycle/Citric Acid Cycle

occurs in mitochondrion, acteyl CoA oxidized to CO2

main fxn of Krebs

produce NADH and FADH2 to enter ETC

overall yield of CAC

2 CO2, 3 NADH, 1 FADH2, 1 GTP

step 1 CAC

rxn: condensation

enzyme: citrate synthase

coenzyme: water

step 1 CAC formula

oxoloacetate + acetyl CoA —→ citryl CoA ——> citrate

step 2 CAC

rxn: isomerization

enzyme: aconitase

coenzyme: water

step 2 CAC formula

citrate —→ cis-aconitate —→ isocitrate

step 3 CAC

rxn: oxidation/decarboxylation

enzyme: isocitrate dehydrogenase

step 3 CAC formula

isocitrate —→ oxalosuccinate —→ a-ketoglutarate

step 4 CAC

rxn: oxidation/decarboxylation

enzyme: a-ketoglutarate dehydrogenase

step 4 CAC formula

a-ketoglutarate + NAD+ + H+ + CoA-SH —→ succinyl CoA + NADH + CO2 + H+

step 5 CAC

rxn: phosphorylation

enzyme: succinyl CoA synthetase

coenzyme: HPO42- + Pi, GDP

step 5 CAC formula

succinyl CoA —→ succinyl phosphate —→ succinate

step 6 CAC

rxn: oxidation

enzyme: succinate dehydrogenase

step 6 CAC formula

succinate —→ fumerate

step 7 CAC

rxn: hydration

enzyme: fumerase

step 7 CAC formula

fumerate —→ L-malatase

step 8 CAC

rxn: oxidation

enzyme: malate dehydrogenase

step 8 CAC formula

L-malate + NAD+ —→ oxaloacetate + NADH + H+

ETC formulas

NADH + H+ ——> NAD+ + 2H+ + 2e-

FADH2 ——> FAD + 2H+ +2e-

4 e- + 4 H+ + O2 —- 2 H2O

ETC

4 enzyme complexes (I, II, III, IV) located along the mitochondrial inner membrane

cytochrome

heme containing protein in which reversible oxidation/reduction of an iron atom occur; heme binds to prevent heme from binding to O2

oxidation phosphorylation

NADH entering ETC = 2.5 ATP

FADH2 entering ETC = 1.5 ATP

amount of ATP prod between glycolysis, transition rxn and Krebs cycle

38 ATP

amount of ATP produced in glucose molecule

10 NADH, 2 FADH2; C6H12O6 + 6O —→ 6 CO2 + 6H2O + 32 ATP (38)