Lipids Fats Oils AP Biology Lipids long term

Lipids: Fats & Oils AP Biology

Lipids long term energy storage concentrated energy AP Biology 2006 -2007

Lipids § Lipids are composed of C, H, O u long hydrocarbon chains (H-C) § “Family groups” Fats (triglycerides) u phospholipids u steroids u § Do not form polymers big molecules made of smaller subunits u not a continuing chain u AP Biology

Fats § Structure: u glycerol (3 C alcohol) + fatty acid § fatty acid = long HC “tail” with carboxyl (COOH) group “head” enzyme H 2 O dehydration synthesis AP Biology

Building Fats § Triacylglycerol 3 fatty acids linked to glycerol u ester linkage = between OH & COOH u hydroxyl AP Biology carboxyl

Dehydration synthesis H 2 O dehydration synthesis enzyme H 2 O AP Biology enzyme HO

Fats store energy § Long HC chain Why do humans like fatty foods? polar or non-polar? u hydrophilic or hydrophobic? u § Function: u energy storage § concentrated w all H-C! § 2 x carbohydrates cushion organs u insulates body u AP Biology § think whale blubber!

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

Unsaturated fats § C=C double bonds in the fatty acids plant & fish fats u vegetable oils u liquid at room temperature u § the kinks made by double bonded C prevent the molecules from packing tightly together AP Biology mono-unsaturated? poly-unsaturated?

Saturated vs. unsaturated AP Biology

Phospholipids § Structure: u glycerol + 2 fatty acids + PO 4 § PO 4 = negatively charged It’s just like a penguin… A head at one end & a tail at the other! AP Biology

Phospholipids § Hydrophobic or hydrophilic? fatty acid tails = hydrophobic u PO 4 head = hydrophillic “attracted to water” u split “personality” u Come here, No, go away! interaction with H 2 O is complex & very important! AP Biology “repelled by water”

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

Why is this important? § Phospholipids create a barrier in water define outside vs. inside u they make cell membranes! u AP Biology

Steroids § Structure: u 4 fused C rings + ? ? § different steroids created by attaching different functional groups to rings § different structure creates different function u examples: cholesterol, sex hormones cholesterol AP Biology

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

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

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