Oxidation stages of fatty acids
What are the main stages of this process?
The oxidation of fatty acids is not so much a chemical as a biochemical process, as this cycle of reactions takes place in the organs of living organisms. The process is quite complex, as it includes many stages. Oxidation of fatty acids in biochemistry is called beta-oxidation. This is no accident – the process received this name as in the carboxyl group (-COOH) during reaction, the third atom of carbon oxidizes, which corresponds to the beta position. The acetyl group (CH₃-CO-) also separates, which contains the first two carbon atoms.
Why oxidation takes place
Fatty acids contain energy which must be released for the correct metabolism in the organism and synthesis of ATP (adenosine triphosphate), without which metabolism is impossible. So there is a metabolic route by which fatty acids are transformed into carbon dioxide and water, with the release of energy supply. The process takes place in mitochondria. Thus all cells apart from nerve cells are capable to a greater or lesser degree of oxidizing fatty acids.
4 main stages of oxidation of fatty acids in the body may be singled out:
- Activation of molecule of fatty acids in the cytosol (the coenzyme A attaches to it with the formation of acyl-S-CoA);
Bonding of the obtained substance with the vitamin-like substance carnitine for the move through the membrane of mitochondria, on the membrane is the respective enzyme containing carnitine – carnitine-actyltransferase-1;
The move of fatty acid through the membrane with the enzyme of transclocase: enzyme of carnitine-acyltransferase-2 once more forms acyl-S-CoA, which is subsequently oxidized.
Direct oxidation of fatty acids is a process that includes the cyclical repetition of 4 reactions:
Oxidation (acyl-S-CoA-dehydrogenase forms);
Hydration (enoil-S-CoA-hydratase is obtained);
Oxidation of the 3ʳᵈ carbon atom (hydroxyacyl-S-CoA-dehydrogenase is formed);
Separation of acetyl-S-CoA and attachment of HS-CoA.
After passing through all the stages, the molecule returns to the first oxidation reaction. The process continues as long as the break of the dicarbon links of the fatty acid can take place. When 2 molecules of acetyl-S-CoA form, the oxidation ends. The molecules formed are oxidized in the Krebs cycle.
Here there are lots of experiments where oxidation of different substances is used too.
How obtained energy is calculated
The energy benefit of the oxidation reaction of these acids can be calculated. The following factors influence it:
The amount of ATP expended on activation of the fatty acid molecule (corresponds to two macroergic bonds – 2 ATP molecules are spent, which are subsequently subtracted from the total number of ATP molecules synthesized in the reaction);
The number of double bonds in the fatty acid (if they are present in the initial molecule, the stage of formation of the double bond in the fatty acid molecule in its oxidation can be skipped);
The number of acetyl-S-CoA coenzymes formed for the reaction (to determine this, the number of carbon atoms in the carbon chain of the acid should be divided by 2);
The number of oxidation cycles that take place completely (the number of possible breaks between dicarbon chains of acid corresponds to the number of possible acts of beta-oxidation).
Depending on this, the final amount of synthesized ATP molecules is determined.
Oxidation of fatty acids is an important biochemical reaction which takes place in the organisms of living creatures. It has a significant influence on the synthesis of ATP molecules, and so it necessary for correct metabolism in the organism.