BCHM 307 1nd Edition Lecture 18 Outline of Last Lecture I Lipids A Functions of Lipids II Fatty Acids A Characteristics of Fatty Acids B Unsaturated Lipids III Essential Fatty Acids IV Triacylglycerol Outline of Current Lecture I Triacylglycerols A Function II Trans fatty Acids A Composition III Phosphoacylglycerols IV Sphingolipids V Non Saponifiable Lipids A Sterols Current Lecture This lecture continues on where we left off with triacylglycerols These lipids can be densely packed due to a lack of hydration They are often used as a storage vessels Triacylglycerols are a great source of energy They can be either fats or oils Their melting point is dependent upon the composition of the esterified fatty acids They have a high degree of unsaturated carbons making them liquid at room temperature Triacylglycerols also do not participate in hydrogen bonding and are non polar molecules Triacylglycerols can be chemically modified to act as solids through the process of hydrogenation This leads to saturation of any cis double bonds When this process is done trans fatty acids form as a by product of the reaction In a trans fatty acid the main difference in structure occurs at the site of the double bond In cis versions of triacylglycerols the hydrogen molecules are attached on the same side of the double bond Trans fatty acids have hydrogen molecules attached on opposite sides of the double bond This makes it impossible for our enzymes to degrade trans fatty acids Phosphoacylglycerols are another type of lipid These lipids are found in the lipid membrane Their structure is centered around phosphatidic acid which is formed through the esterification of glycerol to two fatty acids and phosphoric acid These molecules are amphiphilic in nature They also contain an X group that varies The group is always polar or charged in nature The next type of lipid is called a sphingolipid These are also a class of membrane lipids Their core structure is centered around an amino alcohol chain called a sphingosine The sphingolipid is formed through various linkages The sphingosine base is amide linked to a fatty acid chain forming a ceramide The ceramide has a hydroxyl residue attached to it This residue links with a hydrophilic head group to form the sphingolipid Sphingolipids are also amphiphilic Sphingomyelin is a type of sphingolipid that function in the myelin sheath When the glycolipid isn t properly degraded in sphingomyelin this leads to Tay Sachs disease The other major category of lipids is non saponifiable lipids These lipids do not have ester linkages Sterols such as cholesterol fall under this category Cholesterol is another lipid found in lipid membranes These are very hydrophobic molecules Sterols also function as hormones such as estrogen
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