17. If Jessie has a problem transporting fatty acids into the mitochondria for -

Question

17. If Jessie has a problem transporting fatty acids into the mitochondria for -oxidation, then there may be another consequence that we have not yet uncovered! Consider this question: what do you think would happen to fatty acids that arrive at the liver for -oxidation but then cannot be metabolized because they cannot enter the mitochondria? (Hint: They are not transported back to adipose tissue or excreted in the urine!) A. They are stored as TAGs in the liver. B. They are exported back into the blood and used by the brain. C. They are used by the liver to make glucose. D. They are used by the liver to make ketone bodies.

Explanation / Answer

Ans) they are stored as TAGs in the liver

The fatty acid degradation occurs in the liver by the beta-oxidation. The fatty acids entered into the cytosol of the cell are first activated by converting them to acyl CoA derivatives by acyl CoA synthetases in the in the cytosol. The activated acyl CoA derivatives of fatty acids will not pass through the mitochondrial membrane for beta-oxidation. They are transported to the matrix of mitochondria by the acylcarnitine transporter which is located in the membrane of mitochondria.

If they are not entered into the mitochondria then they are converted to triacylglycerols. The three fatty acids are attached to the glycerol molecule and converted to triacylglycerols which are stored in the liver.

The brain mainly utilizes the glucose and it is a major energy source for the brain. Even though the fatty acids reach to the brain via blood-brain will not use it.

The animals do not have the capacity to convert the fats into carbohydrates (glucose) due to the absence of isocitrate lyase and malate synthase. Only plants have these two enzymes and they can convert the fats into carbohydrates. So the fatty acids are not converted to glucose.

Acetone, acetoacetate and beta hydroxyl butyrate are the ketone bodies and the raw material for the synthesis of ketone bodies is acetyl CoA which is the end product of fatty acid degradation. Ketone body formation occurs in the mitochondria and to produce ketone bodies, fatty acids should degrade but it will happen only when the fatty acids are transported into mitochondria. So the fatty acids are not used to produce ketone bodies.

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