Complex Lipids 13.4-13.8

1. Complex Lipids 13.4-13.8 By: Halie Derr Nick Splitt

2. What are complex lipids? • Complex lipids help to create the main components of membranes. • Complex lipids are also referred to as compound lipids. • They can be classified into two groups: phospholipids and glycolipids.

3. What are phospholipids? (continued) • Phospholipids contain at least one fatty acid, a phosphate group, and sometimes a nitrogenous base. • Two subtypes of phospholipids are glycerophospholipids and sphingolipids. • They are one of the most important components of a membrane. • Most phospholipids are created in the liver and enter the bloodstream.

5. What are glycerophospholipids? • Their structures are similar to that of fats. • They are membrane components of cells distributed throughout the body. • They contain glycerol as the alcohol • Also, carbon 2 of the glycerol is always unsaturated. • They can be broken down into three groups which are esterified by either a fatty acid or a phosphate group which is esterified by another alcohol.

6. What are glycerophospholipids?(continued) • If the alcohol choline is used phosphatidylcholines (lechtin) is created. • Lechtin usually contains linoleic acid in the middle and stearic acid on the end. • Lechtin is a major component of egg yolk, a good emulsifier, and found in mayonnaise. • If an alcohol such as ethanolamine or serine is used it will create cephalins which are very similar to lechtins.

7. What are glycerophospholipids? (continued) • When the alcohol inositol is bonded to a molecule by a phosphate ester bond Phosphatidylinositols (PI) is created. • They can be found in biological membranes and can be used as signaling molecules for chemical communication.

8. (Purple indicates the different alcohols)

9. What are sphingolipids? • Johann Thudichum discovered sphingolipids in 1874 and named them after the Sphinx. • When hydrolyzed, sphingosine substitutes for glycerol in these lipids. • They are common membrane components because they have both hydrophilic and hydrophobic characteristics. • Ceramide is a combination of a fatty acid and sphingosine. • Ceramides are found in sphingolipids.

10. How do sphingomyelins help in the myelin sheath? • Myelin sheaths, the coating of nerve axons in the brain, contain different complex lipids, one of them being sphingomyelins. • Sphingomyelins are the most important lipids in the myelin sheaths of nerve cells. • They are associated with diseases such as multiple sclerosis.

11. What are glycolipids? • Glycolipids are complex lipids that contain carbohydrates and ceramides • There are several different groups of glycolipids, such as gangliosides and cerebrosides • Gangliosides have a more complex carbohydrate structure • Cerebrosides contain mono- or oligosaccharides. • They occur mainly in the brain, accounting for 70% of the brains dry weight and at nerve synapses. • The fatty acid of the ceramide part of the cerebroside contains 18 to 24 carbon chains.

12. What are membranes? • Made up of lipid bilayers • A lipid bilayer is a two-layered structure of complex lipids set tail to tail. • Hydrophobic tails point towards each other • Hydrophilic heads point out from each other enabling them to be close to water. • Membranes have liquid like characteristics because the unsaturated fatty acids prevent tight packing in the lipid bilayer. • An important component of a membrane is cholesterol. • Cholesterol has a similar structure to other membranes

13. What role do lipids play in the structure of membranes? • Complex lipids form membranes around organelles which are small structures inside the cells. • They provide selective transport for nutrient and waste products into and out of cells. • In addition, they separate cells from their external environment. • An important component of complex lipids are the unsaturated fatty acids especially in the lipid bilayer.