5. lipids: 1. have little or no affinity for water 2. contain C, H, O sometimes P 3. H:O never 2:1 4. types – fats, oils, phospholipids, steroids, and waxes neutral lipids (a.k.a. triglycerides, fats, or oils) = 3 fatty acids + 1 glycerol molecule
Lipids • Lipids are composed of C, H, O (same elements as carbs but very diff structure/proportions & therefore very different biological properties) • long hydrocarbon chain • Diverse group • fats • phospholipids • steroids • Do not form polymers • big molecules made of subunit smaller molecules • not a continuing chain
Fats • Structure: what makes them hydrophobic?: carboxyl group • glycerol (3C alcohol) + fatty acid • fatty acid = long HC “tail” with COOH group at “head” dehydration synthesis
Fat • Triacylglycerol(big fat molecule!!) • 3 fatty acids linked to glycerol • ester linkage = between OH & COOH
Fats (Q: what happens when you add oil to water?) • Long HC chain • polar or non-polar? • hydrophilic or hydrophobic? • Function: • energy storage • very rich • 2x carbohydrates • cushion organs • insulates body • think whale blubber! “Let’s go to the video tape!” (play movie here)
Saturated no double bonds found between carbon atoms on the fatty acid chains solid at room temperature at room temp., the molecules are packed closely together high melting point i.e. butter Unsaturated one or more double bonds present between carbon atoms on the fatty acid chains liquid at room temperature at room temp., the molecules cannot pack together closely enough to solidify because of the kinks caused by the double bonds low melting point i.e. olive oil Saturated Fats and Unsaturated Fats
Saturated or Unsaturated? a) b) d) c)
Saturated fats • All C bonded to H • No C=C double bonds • long, straight chain • most animal fats • solid at room temp. (mostly animal fats) • contributes to cardiovascular disease (atherosclerosis) = plaque deposits
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 tightlytogether
i.e. peanut butter, margarine unsaturated fats have been synthetically converted to saturated fats by adding hydrogen prevent lipids from separating out in liquid (oil) form Hydrogenated Fats (TransFats)
Structure of Phospholipids • glycerol + 2 fatty acids + PO4 • PO4 negatively charged • other small molecules may also be attached • adenine (ATP)
this arrangement occurs spontaneously when added to water hydrophobic fatty acids meet “tail-to-tail” hydrophilic head groups interact water major components of all cell membranes The Arrangement of Phospholipids in Cell Membranes
Phospholipids • Hydrophobic or hydrophilic? • fatty acid tails = hydrophobic • PO4 = hydrophilic head • dual “personality” • interaction with H2O is complex • & very important!
Phospholipids in water • Hydrophilic heads attracted to H2O • Hydrophobic tails “hide” from H2O • self-assemble into aggregates • micelle • liposome • early evolutionary stage of cell?
Why is this important? • Phospholipids define outside vs. inside • Where do we find phospholipids in cells? • cell membranes
Phospholipids & cells • Phospholipids of cell membrane • double layer = bilayer • hydrophilic heads on outside • in contact with aqueous solution • hydrophobic tails on inside • form core • forms barrier between cell & external environment
a molecule from which other steroids, including the sex hormones are synthesized contains four fused (interlocking) rings a common component of animal cell membranes high levels of it in the blood may contribute to atherosclerosis Cholesterol, a Steroid
Steroids • ex: cholesterol, sex hormones • 4 fused C rings • different steroids created by attachingdifferentfunctional groups to rings cholesterol
From Cholesterol Sex Hormones • What a big difference a little atom can make!
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
Cholesterol helps keep cell membranes fluid & flexible
Let’s build some Lipids!