Integrated SequencePhysics Chemistry Organic Biology

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The Medical Biochemistry Page - Fatty Acid Oxidation
Advanced topic. Good optional reading comprehension



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Special points of emphasis

Reactions of Alkanes

Reactions of Alkenes

Reactions of Alcohols and Ethers

Lipids

Biological Membranes

The Eukaryotic Cell

Oxidation-Reduction

Oxidation-Reduction in Organic Chemistry

Bioenergetics and Cellular Respiration

The factual basis of the following discussion is a step past the MCAT. The point is to help your general fluency. Read for comprehension. Save memorization for medical school.

Fatty acids are broken down by oxidation at the β-carbon. The process begins on the outer mitochondrial membrane by conversion of the fatty acid and ATP into acyl Coa and AMP by fatty acid synthetase. After a complex transport mechanism into the mitochondrial matrix, the acyl Coa is broken down by a repeating sequence of four reactions : oxidation by FAD (dehydrogenation), hydrolysis, oxidation by NAD+ (conversion of a hydroxyl group into a carbonyl group), then thioloysis at the β-carbon, acyl transfer releasing acetyl CoA and producing a new acyl CoA shortened by two carbon atoms. The pathway from acyl Coa to enol Coa to hydroxyacyl CoA to ketoacyl CoA resembles the pathway in the citric acid cycle of succinate to fumarate to malate to oxaloacetate.




Reactions of Carboxylic Acids and Derivatives

Carbohydrates

Lipids

Bioenergetics and Cellular Respiration

If fat breakdown is predominating over carbohydrate metabolism, then there will be insufficient oxaloacetate (formed from pyruvate) to maintain the citric acid cycle at the necessary rate. In that case the acetyl Coa is diverted in the liver to the formation of ketone bodies. One of the ketone bodies, acetoacetate, is a β-keto acid, so it readily decarboxylates, forming acetone, which can be detected in the breath of a person with high levels of acetoacetate in the blood. Believe it or not, this has been on the MCAT.







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