Syntheses of Other Fatty Acids

by Kevin Ahern, PhD

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    00:00 When we think about other fatty acid reactions, fatty acids longer than 16 carbons are made elsewhere in the cell.

    00:07 They are made in the endoplasmic reticulum and interestingly in the mitochondrion.

    00:13 Unsaturated fatty acids are made by starting with the saturated fatty acids and removing electrons from them using an enzyme known asa desaturase, and the desaturases are found in the endoplasmic reticulum.

    00:28 You can see here the numbering scheme for fatty acids and on the top I have indicated the omega numbering scheme that is used to number carbons starting at the right side of the methyl group and moving inwards.

    00:40 On the bottom, I have indicated the delta numbering scheme which starts with the carboxyl and moves rightwards.

    00:45 Now both systems are used to number fatty acids, and it's interesting to note that in the delta numbering system that the mammalian cells cannot make an unsaturated fatty acid, that is a chemical double bond on any carbons past position 9.

    01:02 Now for our practical purposes that means that we as animals can make oleic acid which has a double bond at position 9. But we can't make linoleic or linolenic acid which have double bonds at positions 12 and 15.

    01:18 So, linoleic acid is shown here the linolenic acid is shown here, and this limitation means that we must have these unsaturated fatty acids in our diet, linoleic and linolenic, because we can't synthesize them. They are known as essential fatty acids.

    01:33 Well, we have gone through now the synthesis and the degradation of fatty acids and with this we have seen that acetyl-CoA is produced in one and used in the other to make them.

    01:44 And as we will see in future lectures, the acetyl-CoA is central to all of lipid metabolism.

    About the Lecture

    The lecture Syntheses of Other Fatty Acids by Kevin Ahern, PhD is from the course Lipid Metabolism.

    Included Quiz Questions

    1. It has multiple enzymatic activities.
    2. It is present in the mitochondrion.
    3. It is only found in human cells.
    4. It catalyzes only the last reaction of the process.

    Author of lecture Syntheses of Other Fatty Acids

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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