Lipids Energy Storage AP Biology Lipids n Lipids

Lipids Energy Storage AP Biology

Lipids n Lipids are composed of C, H, O q n Diverse group q q q n long hydrocarbon chain fats phospholipids steroids Do not form polymers q q big molecules made of smaller subunits not a continuing chain AP Biology

Fat Subunits n Structure: q glycerol (3 C alcohol) + fatty acid n fatty acid = long HC “tail” with COOH group at “head” enzyme dehydration synthesis AP Biology

Building Fats n Triacylglycerol q q AP Biology 3 fatty acids linked to glycerol ester linkage = between OH & COOH

Dehydration Synthesis dehydration synthesis enzyme AP Biology enzyme

Fats Store Energy n Long HC chain q q n polar or non-polar? hydrophilic or hydrophobic? Function: q energy storage n n q q cushion organs insulates body n AP Biology very rich 2 x carbohydrates think whale blubber!

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

Unsaturated Fats n C=C double bonds in the fatty acids q q q plant & fish fats vegetable oils liquid at room temperature n AP Biology the kinks made by double bonded C prevent the molecules from packing tightly together

Saturated vs. Unsaturated AP Biology unsaturated

Phospholipids n Structure: q glycerol + 2 fatty acids + PO 4 n AP Biology PO 4 negatively charged

Phospholipids n Hydrophobic or hydrophilic? q q q fatty acid tails = hydrophobic PO 4 = hydrophilic head dual “personality” interaction with H 2 O is complex & very important! AP Biology

Phospholipids in Water n n Hydrophilic heads attracted to H 2 O Hydrophobic tails “hide” from H 2 O q can self-assemble into “bubbles” n n n bubble = “micelle” can also form bilayer early evolutionary stage of cell? bilayer AP Biology

Why is This Important? n Phospholipids create a barrier in water q q AP Biology define outside vs. inside cell membranes

Phospholipids & Cells n Phospholipids of cell membrane q q double layer = bilayer hydrophilic heads on outside n q hydrophobic tails on inside n q in contact with aqueous solution outside of cell and inside of cell form core forms barrier between cell & external environment AP Biology

Steroids n n ex: cholesterol, sex hormones 4 fused C rings q different steroids created by attaching different functional groups to rings cholesterol AP Biology

Cholesterol n Important cell component q q animal cell membranes precursor of all other steroids n q including vertebrate sex hormones high levels in blood may contribute to cardiovascular disease AP Biology

Cholesterol Important component of cell membrane helps moderate cell membrane fluidity & flexibility AP Biology

From Cholesterol Sex Hormones n What a big difference a few atoms can make! AP Biology

Saturated & Unsaturated Fat Activity n n n Calculate the Bond Energies in Each Fat Molecule… It should prove to you that there is less energy holding one together than the other Bond Energies On the unsaturated fat, q q q H – O = 110 k. Cal/mol C – O = 78 C – C = 80 C = O = 187 C – H = 98 C = 145 AP Biology be sure you only calculate this for 7 Carbons in the chain—at the 7 th Carbon, cross out the last CH 3 group, and just bond a Hydrogen