Biological oxidation is an energy-producing reaction in living cells, and it is coupled with a reduction reaction. This process takes place in mitochondria.

Oxidation is removal/loss of electron and 

Reduction is gain of electron

Electron transfer occurs in four different ways :

1. directly as electrons. 

2. as hydrogen atoms. 

3. as hydroid irons. 

4. through direct communication with oxygen.

 *Reducing equivalent is commonly used to designate a single electron equivalent participating in an oxidation-reduction reaction. 

 The term biological oxidation means the transfer of electrons from the reduced co-enzymes through the respiratory chain to oxygen.

The energy released during this process is trapped as ATP. This coupling of oxidation with phosphorylation is called oxidative phosphorylation. In the body, this oxidation is carried out by successive steps of dehydrogenation.




Enzymes and co-enzymes used  in biological oxidation: 

The enzymes involved in the process of biological oxidation belong to the major class of oxidoreductases. They can be classified into the following groups:

  • oxidases
  • aerobic dehydrogenases 
  •  anaerobic dehydrogenases
  •  Hydro peroxidases
  •  oxygenases

Difference B/W aerobic and anaerobic dehydrogenases:


Some High Energy Compounds:

These compounds when hydrolyzed will release a large amount of energy, which means they have a large Delta G. The high-energy Bond in compounds is usually indicated by a squiggle bond(~).  

Adenosine triphosphate (ATP) and Creatine phosphate (CP) are the two high-energy bonds.

ATP is the universal currency of energy within the living cell. The hydrolysis of ATP to ADP under standard conditions releases -30.5KJ/mol or- 7.3 kcal/mol( Delta G =- 7.3).

The energy in the ATP is used to drive all endergonic reactions. The Energy Efficiency of the cell is comparable to any machine so far invented. ATV captures the chemical energy released by the combustion of nutrients and transfers it to synthetic reactions that require energy

Address sodium-potassium ATPase uses up one-third of all ATP formed. 

ATP is continuously being hydrolyzed and regenerated. An average person addressed consumes and regenerates ATP at a rate of approximately 3 molecules per second which is about 1.5 kg per day!

Creatine phosphate:

Phosphocreatine provides a high-energy reservoir of ATP to regenerate ATP rapidly by the Lohmann's reaction, catalyzed by creatinine kinase enzyme.

The reaction is mitochondrial and of special significance in the myocardium which has a high energy requirement, about 6 kg of ATP.  Energy transfer to the heart myofibrils is by creatinine kinase energy shuttle,  since being the smaller molecule than ATP, CP  can rapidly diffuse from the myocardium to the myofibril.



Note: next post on ETC