Chapter 6 Biological Oxidation. The biochemistry and molecular biology department of CMU. Biological oxidation is the process in which substances (carbohydrate, Lipid, AAs) are oxidized in living organism. Oxidation types: Dehydrogenation Electron lost Oxygenation.
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The biochemistry and molecular biology department of CMU
Biological oxidation is the process in which substances (carbohydrate, Lipid, AAs) are oxidized in living organism.
1. 37℃, pH 7.4, enzymatic reaction.
2. Energy released gradually.
3. Formation of H2O.
4. Formation of CO2 by decarboxylation.
§2 Oxidative Phosphorylation
§4 Shuttle Systems
A chain in the mitochondria consists of a number of redox carriers for transferring hydrogens removed from the substrate to oxygen to form water. The chain is termed a respiratory chain, also called electron transport chain (ETC).
Hydrogen carrier：NAD +
The nicotinamide is the vitamin PP.
FAD: Flavin Adenine Dinucleotide
They contain the riboflavin (Vit B2).
Iron-sulfur centers (Iron-sulfur protein,Fe-S) are prosthetic groups containing 2, 3, 4 or 8 nonheme iron atoms complexed to elemental and cysteine S.
2 Fe colored orange; elemental & Cys S yellow.
Fe3+ + e- Fe2+
Coenzyme Q (CoQ, ubiquinone) is very hydrophobic. It dissolves in the membrane.
Coenzyme Q functions as a mobile e- carrier within the mitochondrial inner membrane.
Cytochromes (Cyt)are proteins with heme prosthetic groups. They absorb light at characteristic wavelengths.
Fe3+ + e- Fe2+
2. O2 issuddenly introduced into the system.
3. Standard redox potential.
Standard reduction potentials for respiratory chain and related electron carriers
The phosphorylation of ADP to ATP coupled to electron transfer from a substrate to molecular oxygen.
Phosphorylation of ADP or GDP to ATP or GTP coupled to the dehydrogenation of an organic substrate.
(number of ATP / 2H)
① NADH → CoQ
② CoQ → Cyt c
③ Cyt aa3→ O2
P/O ratio =3,
3mol ATP / 2H.
P/O ratio =2，
2mol ATP / 2H.
1. Chemiosmotic hypothesis
Spontaneous electron flowthrough each of complexes I, III, & IV is coupled toH+ ejection from the matrix.
Transport of ATP, ADP, & Pi
2.5 ~P bonds synthesized during oxidation of NADH produced in the matrix. (10 H+ pumped; 4 H+ used up per ATP).
1.5 ~P bonds synthesized during oxidation of FADH2 produced in the matrix.
A. Inhibitors of ETC
A compound that disrupts the usual tight coupling between electron transport and phosphorylation of ADP.
A compound that Inhibits electron transport and phosphorylation of ADP.
[ADP]↑→ Oxidative phosphorylation↑
[ADP]↓→ Oxidative phosphorylation↓
antimycin A ( CN-)
Influence of different substrates and inhibitors on quantity consuming oxygen
Na+,K+-ATPase →ATP catabolism → ADP↑ → Oxidative phosphorylation↑ → formation of ATP↑. Formation and catabolism of ATP↑，consuming of O2↑, Generation of Heat↑.
Free radical → mutation of DNA → inhibition of Oxidative phosphorylation → energy↓
βbond △ G0′＝ －32.2KJ
γbond △ G0′＝ －30.5KJ
>30KJ （ 7kcal ）-high energy bonds
AMP~P~PAMP~P + Pi
(ATP ADP + Pi)
AMP~P~PAMP + P~P
(ATP AMP + PPi)
2 ADP ATP + AMP
Nucleoside Diphosphate Kinase catalyzes reversible reactions such as:
ATP + GDPADP + GTP,
ATP + UDPADP + UTP, etc.
The inner membrane of mitochondria is quite impermeable to some molecules and ions.
Pyr, succinate, α-ketoglutarate, malate, citrite, Glu etc.
H+, NADH, NADPH, OAA etc.
Brain, skeletal muscle