University:
California State University, Northridge
Course:
CHEM 100 | Principles of Chemistry
Academic year:

2023
Views:

418

Pages:

1
Author:

Janice G.

Fatty acid oxidation (beta oxidation) Beta oxidation is a procces for fatty acids to obtain energy. First, fatty acids must be activated to from acyl-CoA. After that the fatty acids activated catalyzed by the enzyme acyl-CoA sythetase (Thiokinase). Free fatty acids are generally long chain fatty acids. These long chain fatty acids will be able to enter the mitochondria with the help of the carnitine compound, with the formula (CH3)3N+CH2-CH(OH)- CH2COO-. Neither fatty acids nor CoA are energetic enough to form fatty acyl-CoA directly so the cell increases the chemical reactivity of the fatty acid carboxyl group and invests ATP. The triphosphate group of the ATP molecule is resolved to produce pyrophosphate and the remainder, namely adenosine monophosphate, forms a high-energy anhydride bond with fatty acids and can be broken down by reaction with the thiol group of CoA. The steps for the entry of acyl CoA into mitochondria are explained as follows:  Free fatty acids (FFA) are activated into acyl-CoA catalyzed by the enzyme thiokinase.  After becoming the active form, acyl-CoA is converted by the carnitine palmitoyl transferase I enzyme found in the external mitochondrial membrane into acyl carnitine.  After becoming acyl carnitine, this compound can penetrate the internal mitochondrial membrane.  In the internal mitochondrial membrane there is the enzyme carnitine acyl carnitine translocase which acts as a transporter for acyl carnitine in and carnitine out.  The acyl carnitine that enters the mitochondria then reacts with CoA catalyzed by the carnitine palmitoyltransferase II enzyme in the mitochondrial internal membrane to become acyl CoA and carnitine is released.  The acyl CoA that is already in the mitochondria then enters the beta oxidation process. In beta oxidation, fatty acids enter a series of cycles with 5 process stages and in each process, 2 C atoms are removed with the final result being acetyl CoA. Next, acetyl CoA enters the citric acid cycle. The fatty acids is oxidized to ketones.Fatty acids can be oxidized if they are first activated to acyl-CoA. This activation process requires 2P of energy. (-2P). Once in the mitochondria, acylCoA will undergo the following stages of change:  Acyl-CoA is converted to delta2-trans-enoyl-CoA. At this stage the respiratory chain occurs by producing 2P energy (+2P)  delta2-trans-enoyl-CoA is converted to L(+)-3-hydroxy- acyl-CoA  L(+)-3-hydroxy-acyl-CoA is converted to 3-Ketoacyl-CoA. At this stage the respiratory chain occurs by producing 3P energy (+3P)  Next, acetyl CoA is formed which contains 2 C atoms and acylCoA which has lost 2 C atoms.  In one beta oxidation, 2P and 3P energy is produced so that the total energy for one beta oxidation is 5P. Because fatty acids generally have many C atoms, the remaining acyl-CoA will undergo beta oxidation again and lose another 2 C atoms to form acetyl CoA.  And so on until the last result is 2 acetyl-CoA.  Acetyl-CoA is produced by this beta oxidation Next it will enter the citric acid cycle.

Fatty Acid Oxidation (Beta Oxidation)

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