Fatty acids are primarily degraded through a process called β-oxidation. This process occurs mainly in the mitochondria of cells and involves a series of enzymatic reactions that break down fatty acids into smaller molecules, ultimately producing energy.
The β-Oxidation Pathway Explained
The β-oxidation pathway is the central mechanism for fatty acid degradation. Here's a detailed explanation:
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Activation: Before β-oxidation can begin, fatty acids must be activated. This involves converting them to fatty acyl-CoA derivatives, a process that occurs in the cytoplasm.
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Transport: Fatty acyl-CoA then needs to be transported into the mitochondria. This is facilitated by the carnitine shuttle.
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The β-Oxidation Cycle: Once inside the mitochondria, β-oxidation proceeds through a repetitive four-step cycle:
- Oxidation: The fatty acyl-CoA is oxidized, creating a double bond between the α and β carbons.
- Hydration: Water is added across the double bond, hydrating it.
- Oxidation: The hydroxyl group on the β-carbon is oxidized to a ketone.
- Thiolysis: The molecule is cleaved by thiolase, releasing acetyl-CoA and a fatty acyl-CoA molecule shortened by two carbon atoms.
According to the reference provided, one molecule of acetyl-CoA is released in each round, and the fatty acid backbone is shortened by two carbons.
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Repetition: This cycle repeats until the fatty acid is completely broken down into acetyl-CoA molecules. Each cycle also produces FADH2 and NADH, which are used in the electron transport chain to generate ATP.
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Acetyl-CoA Utilization: The acetyl-CoA molecules then enter the citric acid cycle (Krebs cycle) for further oxidation, generating more ATP, carbon dioxide, and water.
Regulation and Specificity
The efficiency and specificity of fatty acid degradation are tightly regulated. The reference highlights the importance of fatty-acyl CoA oxidase activity in determining the chain-length specificity of the fatty acid backbone. This ensures that fatty acids of varying lengths are processed effectively.
Table Summary
| Step | Description | Location | Products |
|---|---|---|---|
| Activation | Fatty acid converted to fatty acyl-CoA | Cytoplasm | Fatty acyl-CoA |
| Transport | Fatty acyl-CoA transported into mitochondria | Mitochondria | - |
| β-Oxidation Cycle | Repeated cycle of oxidation, hydration, oxidation, and thiolysis | Mitochondria | Acetyl-CoA, FADH2, NADH, Shortened acyl-CoA |
| Citric Acid Cycle | Acetyl-CoA further oxidized to produce energy | Mitochondria | ATP, CO2, H2O |
