Understanding Lipids: Fats & Oils in AP Biology

Slide1AP BiologyLipids: Fats & Oils

Slide2AP Biology2006-2007 Lipids long term energy storage concentrated energy

Slide3AP BiologyLipids  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

Slide4AP BiologyFats  Structure:  glycerol  (3C alcohol)  +   fatty acid  fatty acid = long  HC “tail” with carboxyl (COOH) group “head” dehydration synthesis H 2 O enzyme

Slide5AP BiologyBuilding Fats  Triacylglycerol  3 fatty acids linked to glycerol  ester linkage  = between OH & COOH hydroxyl carboxyl

Slide6AP BiologyDehydration synthesis dehydration synthesis H 2 O H 2 O H 2 O H 2 O enzyme enzyme enzyme

Slide7AP BiologyFats store energy  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! Why do humans like fatty foods?

Slide8AP BiologySaturated 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

Slide9AP BiologyUnsaturated 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 mono-unsaturated? poly-unsaturated?

Slide10AP BiologySaturated vs. unsaturated saturated unsaturated 

Slide11AP BiologyPhospholipids  Structure:  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 !

Slide12AP BiologyPhospholipids  Hydrophobic or hydrophilic?  fatty acid tails =  PO 4  head =  split “personality” interaction with H 2 O is complex &  very important ! “repelled by water” “attracted to water” Come here, No, go away ! Come here, No, go away ! hydrophobic hydrophillic

Slide13AP BiologyPhospholipids in water  Hydrophilic heads “attracted” to H 2 O  Hydrophobic tails “hide” from H 2 O  can self-assemble into “bubbles”  bubble = “micelle”  can also form a  phospholipid bilayer  early evolutionary stage of cell? bilayer water water

Slide14AP BiologyWhy is this important?  Phospholipids create a barrier in water  define outside vs. inside  they make  cell membranes ! Tell them about soap !

Slide15AP BiologySteroids  Structure:  4 fused C rings + ??  different steroids created by attaching   different functional groups  to rings  different structure creates different function  examples:   cholesterol, sex hormones cholesterol

Slide16AP BiologyCholesterol  Important cell component  animal cell membranes  precursor of all other steroids  including vertebrate sex hormones  high levels in blood may contribute to cardiovascular disease

Slide17AP BiologyCholesterol helps keep cell membranes fluid & flexible Important component of cell membrane

Slide18AP BiologyFrom Cholesterol     Sex Hormones  What a big difference a few atoms can make!

Slide19AP Biology2006-2007 Let’s build some Lipids!

Slide20AP Biology2007-2008 Ghosts of Lectures Past (storage)

Slide21AP BiologyPhospholipids & 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 Tell them about soap !