Lipids Homework Questions PDF

Homework Questions for Lipids Part I 1. What is the chemical composition of lipids and give their solubility characteristics? Insoluble and hydrophobic Lipid esters of fatty acids and glycerol Soluble in nonpolar solvents (benzene, chloroform, hexane) Associate together when present in polar solvent...

Homework Questions for Lipids Part I 1. What is the chemical composition of lipids and give their solubility characteristics? Insoluble and hydrophobic Lipid esters of fatty acids and glycerol Soluble in nonpolar solvents (benzene, chloroform, hexane) Associate together when present in polar solvents 2. What is the amphipathic property of lipids and where is it useful? Amphipathic property: both hydrophilicity and hydrophobicity Useful in cell membrane 3. Identify the major classes of lipids Classified based on the chemistry and chemical properties of the lipids Fatty acids, triglycerides, phospholipids, isoprenoids, esters, eicosanoids, glycolipids 4. What are fatty acids? Fatty acids: varying lengths of hydrocarbons (hydrophobic portion) with a carboxylic group (hydrophilic portion) at one end of the chain 5. What are the two factors influencing their characteristics? Chain length: longer chains mean more hydrophobic and higher melting points Degree of unsaturation: more double bonds lower its melting point and increases its fluidity 6. What is the relation of chain length to hydrophobicity and melting point of fatty acids? Chain length: longer chains mean more hydrophobic and higher melting points 7. What is the relation of degree of unsaturation of fatty acids to fluidity and melting point? Degree of unsaturation: more double bonds lower its melting point and increases its fluidity 8. Name some fatty acids found in precorneal tear film Myristic acid: saturated fatty acid Palmitoleic acid: has one double bond Arachidonic acid: has four double bonds Cervonic acid: has six double bonds 9. What are the characteristics of cervonic acid and where is it found? Cervonic acid: has six double bonds and is present abundantly in membranes of retinal photoreceptors 10. How does increasing carbon length and increasing double bonds affect the fatty acid? Increasing carbon length: thickens a membrane and raises its melting point Increasing double bonds: membrane becomes fluid or flexible (enables the fatty acids to slide freely by one another) and lowers its melting point 11. What are the breakdown products of triacylglycerols under normal and abnormal conditions? Also called triglycerides Represent a storage form of fatty acids One triglyceride: three fatty acids bonded to a glycerol molecule using ester bonds Breakdown of triacylglycerols to acetyl CoA- can occur without ketone body formation (occurs in diabetes) 12. What are phospholipids chemically? Phospholipids: when a phosphate ester bonds the glycerol to one of four kinds of polar groups Structure similar to triacylglycerols Most important lipid class: required for the formation and maintenance of all forms of cellular membranes 13. What are the four kinds of polar groups possible in phospholipids? Ethanolamine, choline, serine, inositol 14. What is the membrane structure comprised of? How are the polar head groups arranged? Two lipid layers (bilayer): fatty acid portions face each other Polar head groups: face the aqueous portions of each side of a cell (plasma membrane) or cell chamber (subcellular organelle) Fatty acid composition: varies based on cell’s functional needs 15. Why does the rod outer segment membrane require a high degree of fluidity? What is the fatty acid responsible for this property? For visual transduction function Cervonic acid 16. How does cervonic acid composition vary between red blood cell and rod outer segment? Cervonic acid percent in rod outer segment is almost 6x greater than that of RBC plasma membranes 17. What are isoprenoids? What are the structural components of cholesterol? Built from 5 carbon units- isoprene Composed of cholesterol, vitamin A, and coenzyme Q 18. What is the contribution of cholesterol for ocular functions? Cholesterol makes up only 8% of the lipids of the disc membranes 19. What is chalazion? How does meibomian gland lipid composition vary in this disease? Chalazion: granulomatous inflammation of the eyelid margins With chalazion, meibomian gland lipids are rich in cholesterol 20. What is the source of increased cholesterol production in Chalazion? From the membranes of inflammatory cells such as neutrophils, lymphocytes, and WBCs