2 LipidsLipids areBiomolecules that contain fatty acids or a steroid nucleus.Soluble in organic solvents but not in water.Named for the Greek word lipos, which means “fat.”Extracted from cells using organic solvents.
3 Types of Lipids The types of lipids containing fatty acids are Waxes. Fats and oils (triacylglycerols).Glycerophospholipids.Prostaglandins.Not steroids, as they do not contain fatty acids.
14 Learning Check stearic acid (18 C) saturated Assign the melting points of –17°C, 13°C, and 69°C to the correct fatty acid. Explain.stearic acid (18 C) saturatedoleic acid (18 C) one double bondlinoleic acid (18 C) two double bonds
15 SolutionStearic acid is saturated and would have a higher melting point than the unsaturated fatty acids. Because linoleic has two double bonds, it would have a lower mp than oleic acid, which has one double bond.stearic acid mp 69°C saturatedoleic acid mp 13°Clinoleic acid mp -17°C most unsaturated
20 Learning Check Write a fatty acid with 10 carbon atoms that is: A. saturatedB. monounsaturated omega-3C. monounsaturated omega-6
21 Solution Write a fatty acid with 10 carbon atoms that is: A. saturated CH3—CH2—CH2—CH2—CH2—CH2—CH2—CH2—CH2—COOHB. monounsaturated omega-3CH3—CH2—CH=CH—CH2—CH2—CH2—CH2—CH2—COOHC. monounsaturated omega-6CH3—CH2—CH2—CH2—CH2—CH=CH—CH2—CH2—COOH
30 Melting Points of Fats and Oils A triacylglycerol that is a fatIs solid at room temperature.Is prevalent in meats, whole milk, butter, and cheese.A triacylglycerol that is an oilIs liquid at room temperature.Is prevalent in plants such as olive and safflower.
31 Oils with Unsaturated Fatty Acids Have more unsaturated fats.Have cis double bonds that cause “kinks” in the fatty acid chains.Cannot pack triacylglycerol molecules as close together as in fats.Have lower melting points than saturated fats.Are liquids at room temperature.
35 Chemical Properties of Triacylglycerols The chemical reactions of triacylglycerols are similarto those of alkenes and esters.In hydrogenation, double bonds in unsaturated fatty acids react with H2 in the presence of a Ni or Pt catalyst.In hydrolysis, ester bonds are split by water in the presence of an acid, a base, or an enzyme.
41 Cis and Trans Fatty Acids Unsaturated fatty acids can beCis with bulky groups on same side of C=C.CH3─ (CH2)5 (CH2)7─ COOH cisC=CH HTrans have bulky groups on opposite sides of C=C.CH3─ (CH2)5 HC=C transH (CH2)7─ COOH
42 Trans Fatty Acids and Hydrogenation Are formed during hydrogenation when cis double bonds are converted to trans double bonds.In the body behave like saturated fatty acids.Are estimated to make up 2-4% of our total Calories.Are reported in several studies reported to raise LDL-cholesterol and lower HDL-cholesterol.
43 Learning Check (1) True or (2) False A. There are more unsaturated fats in vegetable oils.B. Vegetable oils have higher melting points than fats.C. Hydrogenation of oils converts some cis-double bonds to trans- double bonds.D. Animal fats have more saturated fats.
44 Solution (1) True or (2) False A. T There are more unsaturated fats in vegetable oils.B. F Vegetable oils have higher melting points than fats.C. T Hydrogenation of oils converts some cis-doublebonds to trans- double bonds.D. T Animal fats have more saturated fats.
45 Hydrolysis In hydrolysis, Triacylglycerols split into glycerol and three fatty acids.An acid or enzyme catalyst is required.+3+3
46 Saponification and Soap Is the reaction of a fat with a strong base.Splits triacylglycerols into glycerol and the salts of fatty acids.Is the process of forming “soaps” (salts of fatty acids).With KOH gives softer soaps.
48 Learning Check 1. Glycerol and 3 oleic acids 2. Glyceryl tristearate What products are obtained from the complete hydrolysis of glyceryl trioleate?1. Glycerol and 3 oleic acids2. Glyceryl tristearate3. Glycerol and 3 stearic acids
49 SolutionWhat products are obtained from the complete hydrolysis of glyceryl trioleate?1. Glycerol and 3 oleic acids
50 Learning CheckWrite the product of the following reaction.+ 3
52 Glycerophospholipids Glycerophospholipids areThe most abundant lipids in cell membranes.Composed of glycerol, two fatty acids, phosphate and an amino alcohol.Fatty acidGlycerolFatty acidPO4Aminoalcohol
53 Glycerophospholipids Are Polar A glycerophospholipid hasTwo nonpolar fatty acid chains.A phosphate group and a polar amino alcohol.CH3│HO−CH2−CH2−N−CH HO−CH2−CH2−NH3│choline CH ethanolamine+NH3│ Amino alcoholsHO−CH2−CH−COO−serine
56 Learning Check Identify each as a A. fatty acid B. triacylglycerol C. amino alcohol D. glycerophospholipid1. glyceryl trioleate2. cephalin3. choline4. palmitic acid
57 Solution Identify each as a A. fatty acid B. triacylglycerol C. amino alcohol D. glycerophospholipid1. glyceryl trioleate B. triacylglycerol2. cephalin D. glycerophospholipid3. choline C. amino alcohol4. palmitic acid A. fatty acid
58 Learning Check Identify the components and type of glycerophospholipid ║CH2−O −C −(CH2)16 −CH3+O NH3║ │CH2−O −P −O − CH2−CH−COO-│O-
59 Solution Identify the components and type of glycerophospholipid O ║ CH2−O −C −(CH2)16 −CH3O 2 stearic acids+O NH3║ │ type = cephalinCH2−O −P −O − CH2−CH−COO-│ serineO-phosphate amino alcohol
61 Sphingolipids Sphingolipids Are similar to phospholipids. Contain sphingosine (a long-chain amino alcohol), a fatty acid, phosphate, and a small amino alcohol.Have polar and nonpolar regions.fatty acidsphingosinePO4aminoalcohol
62 Sphingosine Sphingosine is a long-chain unsaturated amino alcohol. CH3−(CH2)12 −CH=CH−CH−OH│CH−NH2CH2−OHsphingosine
66 Gangliosides Gangliosides Are similar to cerebrosides, but contain two or more monosaccharides.Are important in neurons.Act as receptor for hormones and viruses.Can accumulate and cause genetic diseases.
76 Learning Check Match the components of the cholesterol molecule with the following:___ carbon chain ___hydroxyl group___ steroid nucleus ___methyl groupDBAC
77 Solution Match the components of the cholesterol molecule with the following:D carbon chain A hydroxyl groupC steroid nucleus B methyl groupDBAC
78 Bile Salts Bile salts Are synthesized in the liver from cholesterol. Are stored in the gallbladder.Are secreted into the small intestine.Have a polar and a nonpolar regionMix with fats to break them part.Emulsify fat particles to provide large surface area.
84 Adrenal Corticosteroids Adrenal corticosteroids are steroid hormones thatAre produced by the adrenal glands located on the top of each kidney.Include aldosterone, which regulates electrolytes and water balance by the kidneys.Include cortisone, a glucocorticoid, which increases blood glucose level and stimulates the synthesis of glycogen in the liver.
90 Cell Membranes Cell membranes Separate cellular contents from the external environment.Consist of a lipid bilayer made of two rows of phospholipids.Have an inner portion made of the nonpolar tails of phospholipids with the polar heads at the outer and inner surfaces.
91 Fluid Mosaic Model of Cell Membranes The lipid bilayerContains proteins, carbohydrates, and cholesterol.Has unsaturated fatty acids that make cell membranes fluid-like rather than rigid.Has proteins and carbohydrates on the surface that communicate with hormones and neurotransmitters.
93 Transport Through Cell Membranes The transport of substances through cellMembranes involvesDiffusion (passive transport), which moves particles from a higher to a lower concentration.Facilitated transport, which uses protein channels to increase the rate of diffusion.Active transport, which moves ions against a concentration gradient.