Lipids energy storage 2006-2007 1

Lipids: Triglycerides, Steroids, Phospholipids 2

Lipids composed of C, H, O 3 classes Do not form polymers long hydrocarbon chain = energy! 3 classes Triglycerides [fat, oil, wax] Steroids [cholesterol, hormones] Phospholipids [membranes] Do not form polymers Macromolecules made of smaller subunits not a chain of repeating monomers Made of same elements as carbohydrates but very different structure/ proportions & therefore very different biological properties 3

dehydration synthesis Triglycerides [fats] Structure: glycerol (3C alcohol) + fatty acids fatty acid = long HC “tail” with COOH group at “head” enzyme Look at structure… What makes them hydrophobic? Note functional group = carboxyl dehydration synthesis 4

Building Fats Triacylglycerol 3 fatty acids linked to glycerol ester linkage = between OH & COOH BIG FAT molecule!! 5

Dehydration synthesis enzyme Pulling the water out to free up the bond enzyme enzyme 6

Why do humans like fatty foods? Fats store energy Long HC chain polar or non-polar? hydrophilic or hydrophobic? Function: energy storage very rich 2x carbohydrates cushion organs insulates body think whale blubber! What happens when you add oil to water Why is there a lot of energy stored in fats? • big molecule • lots of bonds of stored energy So why are we attracted to eating fat? Think about our ancestors on the Serengeti Plain & during the Ice Age. Was eating fat an advantage? 7

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 Mostly animal fats 8

Unsaturated fats C=C double bonds in the fatty acids plant & fish fats vegetable oils liquid at room temperature the kinks made by double bonded C prevent the molecules from packing tightly together Mostly plant lipids Think about “natural” peanut butter: Lots of unsaturated fats Oil separates out Companies 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 it Affect nutrition? mono-unsaturated? poly-unsaturated? 9

Saturated vs. unsaturated  10

Steroids ex: cholesterol, sex hormones 4 fused C rings different steroids created by attaching different functional groups to rings cholesterol 11

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 12

Cholesterol Important component of cell membrane helps keep cell membranes fluid & flexible 13

From Cholesterol  Sex Hormones What a big difference a few atoms can make! Same C skeleton, different functional groups 14

It’s just like a penguin… Phospholipids Structure: glycerol + 2 fatty acids + PO4 PO4 negatively charged It’s just like a penguin… A head at one end & a tail at the other! 15

It likes water & also pushes it away! Phospholipids Hydrophobic or hydrophilic? fatty acid tails = hydrophobic PO4 = hydrophilic head dual “personality” It likes water & also pushes it away! interaction with H2O is complex & very important! 16

Phospholipids in water Hydrophilic heads attracted to H2O Hydrophobic tails “hide” from H2O can self-assemble into “bubbles” bubble = “micelle” can also form bilayer early evolutionary stage of cell? bilayer 17

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 Phospholipid bilayer Note other molecules in membrane… Tell them about soap! 18

Why is this important? Phospholipids create a barrier in water define outside vs. inside cell membranes 19