Oxidative decarboxylation in Krebs cycle: citrate (6C) —> a-ketoglutarate (5C)
CO2 and NADH formed
A-ketoglutarate (5C) —> oxaloacetate (4C)
3 dehydrogenation reactions form FADH2 and 2NADH
decarboxylation
substrate level phosphorylation (ADP to ATP)
Products of Krebs cycle: 4 CO2, 6 NADH, 2 FADH2, 2 ATP
Oxidativephosphorylation only takes place in the presence of oxygen.
during oxidative phosphorylation, hydrogenatoms dissociate from NADH and FADH2, split to form H+ and electrons.
H+ ions pumped across the innermitochondrialmembrane via active transport from the mitochondrial matrix into the inter membrane space.
Electrons are transported down the electron transport chain containing electron carriers with progressivelylowerenergylevels, releases energy that pumps H+ across inner mitochondrial membrane.
H+ ion concentration is high in the intermembranespace, establishing a proton concentration gradient.
H+ ions diffuse down the concentration across the inner mitochondrial membrane through ATP synthase back into the mitochondrialmatrix.Chemiosmosis takes places, proton motive force is used to drive ATP synthesis (ATP synthase catalyses ADP to ATP).
oxygen acts as the final electron acceptor to accept electrons from the electron transport chain and H+ ions to form water.
3 ATP is formed per NADH
2 ATP is formed from FADH2
total ATP formed from oxidative phosphorylation: 34 ATP per glucose
Anaerobic respiration consists of glycolysis followed by fermentation.
Alcohol fermentation occurs in yeast and some bacteria
In alcohol fermentation:
pyruvate is decarboxylated into ethanal/acetaldehyde (by pyruvate decarboxylase)
ethanal/acetaldehyde is reduced to ethanol (by alcohol dehydrogenase), NADH loses H+ (oxidised) in the process
NAD+is reformed
2 ATP is formed from glycolysis
Lactic acid fermentation occurs in bacteria,fungi, musclecells.
In lactic acid fermentation:
pyruvate is reduced to lacticacid (by lactate dehydrogenase), NADH is oxidised back to NAD+
2 lactate formed per glucose
2 ATP formed during glycolysis
Importance of anaerobic respiration:
synthesise small amount of ATP
regenerate NAD+
Role of NAD+ and FAD+
accepts high energy electrons and protons to form NADH and FADH2
carries electrons from glycolysis, link reaction and Krebs cycle to the electron transport chain
acts as a coenzyme during oxidation by dehydrogenation
role of oxygen:
final electron acceptor, combines with electrons and H+ ions to form water
allows oxidative phosphorylation to continue to generate ATP
NAD+ and FAD regenerated, can pick up more electrons and protons from glycolysis, link reaction and Krebs cycle
removes H+ from matrix, contributes to generation of proton gradient across inner mitochondrial membrane
less glucose needed for aerobic respiration than anaerobic respiration:
aerobic respiration produces 38netatp per glucose whereas anaerobic 2 net atp per glucose (substrate level phosphorylation during glycolysis)
oxidative phosphorylation synthesises 34 net atp in presence of oxygen, no oxidative phosphorylation during anaerobic conditions