4 Lipids Lipids are composed of C, H, O Diverse group fat long hydrocarbon chainDiverse groupfatsphospholipidssteroidsDo not form polymersbig molecules made of smaller subunitsnot a continuing chainfatMade of same elements as carbohydrates but very different structure/ proportions & therefore very different biological properties
5 dehydration synthesis Fat subunitsStructure:glycerol (3C alcohol) + fatty acidfatty acid = long HC “tail” with COOH group at “head”enzymeLook at structure… What makes them hydrophobic?Note functional group = carboxyldehydration synthesis
6 Building Fats Triacylglycerol 3 fatty acids linked to glycerol ester linkage = between OH & COOHBIG FAT molecule!!
7 Dehydration synthesis enzymePulling the water out to free up the bondenzymeenzyme
8 Why do humans like fatty foods? Fats store energyLong HC chainpolar or non-polar?hydrophilic or hydrophobic?Function:energy storagevery rich2x carbohydratescushion organsinsulates bodythink whale blubber!What happens when you add oil to waterWhy is there a lot of energy stored in fats?• big molecule• lots of bonds of stored energySo why are we attracted to eating fat?Think about our ancestors on the Serengeti Plain & during the Ice Age. Was eating fat an advantage?
9 Saturated fats All C bonded to H No C=C double bonds long, straight chainmost animal fatssolid at room temp.contributes to cardiovascular disease (atherosclerosis) = plaque depositsMostly animal fats
10 Unsaturated fats C=C double bonds in the fatty acids plant & fish fats vegetable oilsliquid at room temperaturethe kinks made by double bonded C prevent the molecules from packing tightly togetherMostly plant lipidsThink about “natural” peanut butter:Lots of unsaturated fats Oil separates outCompanies want to make their product easier to use:Stop the oil from separating Keep oil solid at room temp.Hydrogenate it = chemically alter to saturate itAffect nutrition?mono-unsaturated?poly-unsaturated?
12 It’s just like a penguin… PhospholipidsStructure:glycerol + 2 fatty acids + PO4PO4 negatively chargedIt’s just like a penguin…A head at one end& a tail at the other!
13 It likes water & also pushes it away! PhospholipidsHydrophobic or hydrophilic?fatty acid tails = hydrophobicPO4 = hydrophilic headdual “personality”It likes water & also pushes it away!interaction with H2O is complex & very important!
14 Phospholipids in water Hydrophilic heads attracted to H2OHydrophobic tails “hide” from H2Ocan self-assemble into “bubbles”bubble = “micelle”can also form bilayerearly evolutionary stage of cell?bilayer
15 Why is this important? Phospholipids create a barrier in water define outside vs. insidecell membranes
16 Phospholipids & cells Phospholipids of cell membrane double layer = bilayerhydrophilic heads on outsidein contact with aqueous solution outside of cell and inside of cellhydrophobic tails on insideform coreforms barrier between cell & external environmentPhospholipid bilayerNote other molecules in membrane…
17 Steroids ex: cholesterol, sex hormones 4 fused C rings different steroids created by attaching different functional groups to ringscholesterol
18 Cholesterol Important cell component animal cell membranes precursor of all other steroidsincluding vertebrate sex hormoneshigh levels in blood may contribute to cardiovascular disease
19 Cholesterol Important component of cell membrane helps keep cell membranes fluid & flexible
20 From Cholesterol Sex Hormones What a big difference a few atoms can make!Same C skeleton, different functional groups