Lipids: Functions

by Kevin Ahern, PhD

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    Besides the lipids involved in energy storage and membrane components, other class of lipids play very important roles in regulating processes in the body. These lipids will be the subject of this lecture. This will include molecules that are derived from cholesterol such as the steroids, the bile and bile acids, as well as other molecules that are derived from fatty acids, such as the prostaglandins, thromboxanes, the leukotrienes. And last I will talk about the fat-soluble vitamins which are derived from a combination of the two. Now if we look at the structure we see on the screen, this general structure is referred to as the sterol. There are many compounds that have structures related to this, one of them being for example cholesterol. Now we give a general name to the various sterols that are found in different organisms, so for example phystosterols are known as plant sterols, whereas zoosterols are known as animal sterols. The sterols are assembled from relatively simple compounds. Now the simple compounds that make up sterols are called isoprenoids and they derive their name from the fact that they have five carbon building blocks. The two five carbon building blocks that are used to make all of the sterols are known, as on the left, dimethylallylpyrophosphate and on the right, isopentenylpyrophosphate. These two molecules are joined together in a variety of combinations to make the higher order structures that come to be the sterols. You can see for example if you put these two molecules from the last slide together, you create a ten carbon compound called geranylpyrophosphate. If we add one more of the five carbon building blocks, we create farnesylpyrophosphate, now that has fifteen carbons. And if we take two of those farnesylpyrophosphates and join them together, we create a linear...

    About the Lecture

    The lecture Lipids: Functions by Kevin Ahern, PhD is from the course Biochemistry: Basics. It contains the following chapters:

    • Sterols - Overview
    • Steroid Hormones
    • Additional Lipids
    • Fat Soluble Vitamins

    Included Quiz Questions

    1. ...are made from isoprenoids.
    2. ...are not found in plants.
    3. ...are most commonly found in the cytoplasm of cells.
    4. ...are made from ketone bodies.
    1. ...is ultimately made from acetyl-CoA.
    2. ...narrows the Tm of membranes containing it.
    3. ...must be in the diet of mammals.
    4. ...is used to make squalene.
    1. ...are made from cholesterol.
    2. ...are derived from vitamin D.
    3. ...require an aromatase to make androgens from estrogens.
    4. ...are very water soluble.
    1. ...are derived from arachidonic acid.
    2. ...are precursors of the eicosanoids.
    3. ...are broken down by cyclooxygenases.
    4. ...have synthesis stimulated by aspirin and NSAIDs.
    1. ...vitamin A is essential for vision.
    2. ...vitamin C is made from glucose.
    3. ...vitamin E helps to stimulate cellular oxidation.
    4. ...vitamin K is used in surgery to reduce the likelihood of blood.

    Author of lecture Lipids: Functions

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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