| Location | Mitochondrial matrix of most body cells (especially liver and muscle) | Mitochondrial matrix of liver cells only |
| Function | Breaks down fatty acids into acetyl-CoA to generate energy (ATP) | Converts excess acetyl-CoA into ketone bodies during prolonged fasting or low carbohydrate intake |
| Primary Products | Acetyl-CoA, NADH, FADH₂ | Ketone bodies |
| Energy Yield | High ATP yield from oxidation of long-chain fatty acids | No direct ATP from ketogenesis; ketones serve as alternative energy sources for other tissues |
| Triggers | Body needs ATP from fat (e.g., fasting, exercise) | Glucose is scarce, and acetyl-CoA accumulates due to ongoing beta-oxidation |