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Chapter 5 Macromolecules-Lipids

Chapter 5 Macromolecules-Lipids . Lipids . Lipids are composed of C, H, O long hydrocarbon chains (H-C) “Family groups” fats phospholipids steroids Do not form polymers big molecules made of smaller subunits not a continuing chain. enzyme. H 2 O. Fats . Structure:

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Chapter 5 Macromolecules-Lipids

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  1. Chapter 5 Macromolecules-Lipids

  2. Lipids • Lipids are composed of C, H, O • long hydrocarbon chains (H-C) • “Family groups” • fats • phospholipids • steroids • Do not form polymers • big molecules made of smaller subunits • not a continuing chain

  3. enzyme H2O Fats • Structure: • glycerol (3C alcohol) +fatty acid • fatty acid = long HC “tail” with carboxyl (COOH) group “head” • 12-20 carbons- Always an even number. • These extensive chains make fats very nonpolar. dehydration synthesis

  4. Fats (Tricylglycerols) • Fats constructed of two kinds of smaller molecules • Glycerol - Three carbons covalently bound to one another, each with a single hydroxyl group.

  5. Function of Fats • Energy storage. 1 gram of fat stores more than 2x the energy of 1 gram of carbohydrate. • Insulation. Fat is an exceptional thermal and electrical insulator.

  6. Fatty acid (palmitic acid) Glycerol (a) Dehydration reaction in the synthesis of a fat Formation of Fats • Fats form as a result of a dehydration reaction between glycerol and a fatty acid. • This kind of linkage is called an ester linkage. • Ester linkage = between OH & COOH

  7. Fig. 5-11b Ester linkage (b) Fat molecule (triacylglycerol)

  8. enzyme enzyme enzyme H2O H2O H2O H2O Dehydration synthesis dehydration synthesis

  9. Fats store energy Why do humanslike fatty foods? • Long HC chain • polar or non-polar? • hydrophilic or hydrophobic? • Function: • energy storage • concentrated • all H-C! • 2x carbohydrates • cushion organs • insulates body • think whale blubber!

  10. Saturated v. Unsaturated Fats • Saturated fats are composed of fatty acid chains that contain no double bonds. • Saturated with hydrogens. • Unsaturated fats are composed of fatty acid chains with double bonds. • They are not saturated. • Naturally occurring fatty acid chains are all cis-fats.

  11. Saturated fats • All C bonded to H • No C=C double bonds • long, straight chain • most animal fats • solid at room temp. • contributes to cardiovascular disease (atherosclerosis) = plaque deposits

  12. Unsaturated fats • C=C double bonds in the fatty acids • plant & fish fats • vegetable oils • liquid at room temperature • the kinks made by doublebonded C prevent the molecules from packing tightly together mono-unsaturated? poly-unsaturated?

  13. Fig. 5-12b Structural formula of an unsaturated fat molecule Oleic acid, an unsaturated fatty acid cis double bond causes bending (b) Unsaturated fat

  14. Structural formula of a saturated fat molecule Fig. 5-12a Stearic acid, a saturated fatty acid (a) Saturated fat

  15. Saturated vs. unsaturated saturated unsaturated 

  16. Phospholipids & cells • Phospholipids of cell membrane • double layer = bilayer • hydrophilic heads on outside • in contact with aqueous solution outside of cell and inside of cell • hydrophobic tails on inside • form core • forms barrier between cell & external environment

  17. Phospholipids • Structure: • glycerol + 2 fatty acids + PO4 • PO4 = negatively charged It’s just like apenguin… A head at one end & a tail at the other!

  18. Phospholipids • Hydrophobic or hydrophilic? • fatty acid tails = • PO4 head = • split “personality” hydrophobic hydrophillic “attracted to water” interaction with H2O is complex & very important! “repelled by water”

  19. Choline Phosphate Hydrophilic head Fig. 5-13 Glycerol Fatty acids Hydrophobic tails Hydrophilic head Hydrophobic tails Space-filling model Phospholipid symbol (a) (b) (c) Structural formula

  20. Phospholipid

  21. Phospholipids in water • Hydrophilic heads “attracted” to H2O • Hydrophobic tails “hide” from H2O • can self-assemble into “bubbles” • bubble = “micelle” • can also form a phospholipidbilayer water bilayer water

  22. Phospholipids • Similar to fats in structure. • Three components • Glycerol • 2 Fatty acids • Phosphate group • Phosphate group replaces the 3rd fatty acid in tricylglycerol

  23. Phospholipid Properties • Phospholipids are amphipathic. • In an aqueous environment the hydrophobic tails of phospholipids are pushed together while the heads interact with water and each other. • Because of this, phospholipids spontaneously take on a characteristic bilayer arrangement.

  24. Functional Importance of Phospholipids • Phospholipid bilayer is the primary component of biological membranes http://academic.brooklyn.cuny.edu/biology/bio4fv/page/lipos.gif

  25. Importance of Phospholipids • Water and ions cannot freely diffuse through the bilayer. • Phospholipids keep the inside of the cell inside the cell and the outside of the cell outside the cell. • There are proteins embedded in the phospholipidbilayer that allow select polar molecules and ions through the bilayer.

  26. Why is this important? • Phospholipids create a barrier in water • define outside vs. inside • they make cell membranes!

  27. Steroids • Steroids are another class of lipids. • They are hydrophobic and always have the same root structure. • Functional groups attached to the steroid structure greatly influence the biological action of the steroid.

  28. Steroids • Structure: • 4 fused C rings • different steroids created by attachingdifferentfunctional groups to rings • different structure creates different function • examples: • Cholesterol • Sex hormones cholesterol

  29. Important Steroids http://www.chem.ucalgary.ca/courses/351/Carey5th/Ch26/ch26-5-1.html

  30. Cholesterol • Important cell component • animal cell membranes • precursor of all other steroids • including vertebrate sex hormones • high levels in blood may contribute to cardiovascular disease

  31. Cholesterol Important component of cell membrane helps keep cell membranes fluid & flexible

  32. From Cholesterol  Sex Hormones • What a big difference a few atoms can make!

  33. Lipids!

  34. Tricylglycerol Glycerol Triacylglycerol Fatty Acid

  35. Review • What two components make up fats? • What is an Ester Linkage? • Triacylglycerol (triglyceride):

  36. Saturated Fats Vs. Unsaturated Fats • Saturated: • Unsaturated:

  37. Function and Storage of Fat • Function: • Storage: Adipose Tissue

  38. Phospholipids • Structure: • How do they behave in water? • Relation to cell membrane:

  39. Steroids • Structure: • Ex) Cholesterol:

  40. How are Phospholipids different than fats? • The phosphate is charged. • This makes that part of the molecule _________________________ • The fatty acid chains are _________________________

  41. Function of Steroids • Component of cell membranes (cholesterol). • Hormones

  42. Questions to Consider • Steroids including cholesterol are do not usually travel alone in the bloodstream. Why not? • Suppose a phopholipid membrane surrounded an oil droplet. It frequently does in plant seeds. What form might the membrane take on in these cases?

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