Goals of the Day… Lipids… Types of fatty acid lipids Characteristics of fatty acids (# of carbons, saturated, monounsaturated, polyunsaturated, omega 3 vs. omega 6, etc.). Recognize: prostoglandins, triacyglycerols, glycerophospohlipids, sphingolipids, and steroids. Next Class… Steroids & Reactions of triglycerides (forming; H2; H2O; NaOH)

Lipids Lipids are biomolecules 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 nonpolar organic solvents. natural components of cell membranes, fat-soluble vitamins, and steroid hormones.

Lipids There are 2 types of lipids; those that contain the structural component of a fatty acid; and those that contain the structural component of a four member steroid molecule.

Types of Lipids The lipids that contain fatty acids are waxes, fats and oils (triacylglycerols), glycerophospholipids, and prostaglandins. The types of lipids that do not contain fatty acid chains are steroids.

Types of Fatty Acid Lipids

Learning Check Which lipids contain the alcohol glycerol? A. steroids and waxes B. triacylglycerols and glycerophospholipids C. sphingolipids and glycerophospholipids D. glycerophospholipids and waxes

Solution A. steroids and waxes B. triacylglycerols and glycerophospholipids C. sphingolipids and glycerophospholipids D. glycerophospholipids and waxes

Fatty Acids Fatty acids contain long-chain hydrocarbons with a carboxylic acid. typically contain 12 to 18 carbon atoms. are insoluble in water. can be saturated or unsaturated.

Ways to show Fatty Acid structures The formulas for fatty acids are written as condensed structural formulas. skeletal formulas. Insert structures of lauric acid pg 600, both condensed structural formula and skeletal formulas

Saturated Fatty Acids Saturated fatty acids have only single C—C bonds. molecules that fit closely together in a regular pattern. have properties similar to alkanes.

Some Saturated Fatty Acids

Unsaturated Fatty Acids have one or more double bond. that are naturally occurring have one or more cis double bond insert picture of cis and trans fatty acid from top of pg 602

Monounsaturated Fatty Acids Unsaturated fatty acids with one double bond are called monounsaturated fatty acids. Insert table 17.1 monounsaturated fatty acids.

Polyunsaturated Fatty Acids Unsaturated fatty acids with more than one double bond are called polyunsaturated fatty acids.

Properties of Saturated Fatty Acids fit closely together in a regular pattern. have significant dispersion forces between chains. have higher melting points. are solids at room temperature.

Properties of Unsaturated Fatty Acids “kinks” in chain Unsaturated fatty acids have “kinks” in the fatty acid chains. do not pack closely. have fewer attractions between chains. have lower melting points. are liquids at room temperature.

Learning Check A. oleic acid B. stearic acid C. linoleic acid Assign the melting point (mp) of −17°C, 13°C, or 69°C to each one of the following 18-carbon fatty acids, and list the fatty acids in order from highest to lowest melting point. Explain. A. oleic acid B. stearic acid C. linoleic acid

Solution Stearic acid is saturated and would have a higher melting point than the unsaturated fatty acids. Oleic acid, which has one double bond, has a higher mp than linoleic acid, which has two double bonds. B. stearic acid mp 69°C saturated A. oleic acid mp 13°C unsaturated with one double bond C. linoleic acid mp −17°C unsaturated with two double bonds

Essential Fatty Acids: Omega-3 and Omega-6 Fatty Acids Fish and vegetable oils have high levels of unsaturated fats. In vegetable oils, they are mostly omega-6 with the first at C6. Linoleic acid In fish oils, they are mostly omega-3 with the first at C3. CH3─CH2─(CH═CH─CH2)3─(CH2)6─COOH 1 3 Linolenic acid

Omega-6 and Omega-3 Fatty Acids

Omega-3 Fatty Acids Omega-3 fatty acids lower the tendency of blood platelets to stick together, thereby reducing the possibility of blood clots. can help reduce risk of heart disease. are found in salmon, tuna, and herring.

Which of these are: saturated, monounsaturated omega-3 and monounsaturated omega-6? CH3—CH2—CH2—CH2—CH2—CH2—CH2—CH2—CH2—COOH B. C.

Solution A. saturated (no double bonds) CH3—CH2—CH2—CH2—CH2—CH2—CH2—CH2—CH2—COOH B. monounsaturated omega-3 (double bond at 3) C. monounsaturated omega-6 (double bond at 6)

Fatty Acid Summary… Fatty acids can be: Saturated Unsaturated Polyunsaturated Omega 3 or omega 6

Various Fatty Acids…

Fatty Acid Derivatives… Waxes (contain 1 fatty acid & 1 alcohol) Prostoglandins (contains a ring) Triacylglycerols or triglycerides (contain 3 fatty acids & glycerol) Glycerophospholipid (contains glycerol, 2 fatty acids, a phosphate group & an amino alcohol). Sphingolipids (contains sphingosine instead of glycerol as the backbone)

Waxes Waxes are esters of saturated fatty acids and long-chain alcohols each containing 14 to 30 carbon atoms. coatings that prevent loss of water from leaves of plants.

Typical Waxes

Prostaglandins Prostaglandins have 20 carbon atoms in their fatty acid chains. differ by the substituents attached to the 5-carbon ring & # of double bonds on the chain.

Prostaglandins and Physiological Effects Prostaglandins have potent physiological effects. Some increase blood pressure. Some lower blood pressure. Some stimulate contractions and relaxation of smooth muscle in the uterus during the birth process and menstrual cycle. When tissues are injured, arachidonic acid in the blood is converted to PGE1 and PGF2 that produce inflammation and pain in the area.

NSAIDs and Prostaglandins Several nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin, block production of prostaglandins decreasing pain, inflammation, and fever.

NSAIDs and Prostaglandins Other NSAIDs include naproxen (Aleve and Naprosyn), ketoprofen (Actron), and nabumetone (Relafen). Long-term use of such products can result in liver, kidney, and gastrointestinal damage.

Prostoglandin Summary: Recognize a prostoglandin structure. Know they cause inflammation (to let us know that something is wrong in an area of the body so we can take the aspirin & get things better)! 

Fats and Oils: Triacylglycerols Fats and oils are also called triacylglycerols. triesters of glycerol. produced by esterification. formed when the hydroxyl groups of glycerol react with the carboxyl groups of fatty acids. a major form of energy storage for animals. Insert picture of polar bear pg 608

Tricylglycerols In a tricylglycerol, glycerol forms ester bonds with three fatty acids. Insert structure top pg 608 as shown:

Types of triacylglycerols… Simple (all three fats are the same) Mixed (there are 2-3 different fats)

Formation of a Mixed Triacylglycerol Most naturally occurring fats and oils are mixed triacylglycerols that contain glycerol bonded by ester bonds to two or three different fatty acids, typically palmitic acid, linoleic acid, and stearic acid. One possible structure follows.

Learning Check How many carbon atoms are in each fatty acid chain in the following triacylglycerol? Which is unsaturated? Is this simple or mixed?

Solution 18 carbons 18 carbons (unsaturated) 14 carbons It is a mixed triacylglycerol. 

Melting Points of Fats and Oils A triacylglycerol that is usually called a fat is solid at room temperature. is prevalent in meats, whole milk, butter, and cheese. A triacylglycerol that is usually called an oil is liquid at room temperature. is prevalent in plants, such as olive and safflower.

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 closely together as in fats. have lower melting points than do saturated fats. are liquids at room temperature.

Triacylglycerol with Unsaturated Fatty Acids Unsaturated fatty acid chains have kinks that do not allow close packing, such as those in olive oil.

Saturated and Unsaturated Fatty Acids In Fats and Oils Vegetable oils are liquids at room temperature because they have a higher percentage of unsaturated fatty acids than do animal fats.

Recognize the difference… Oil: at room temperature, it is a viscous liquid. Triacylglyceride that has unsaturation, so has a low melting point. Fat: at room temperature, it is a solid. Triacylclyceride that is saturated, so has a higher melting point. Wax: Contains an ester of a “fat” and an alcohol.

Glycerophospholipids Glycerophospholipids, the most abundant lipids in cell membranes, contain two fatty acids, which form ester bonds with the first and second hydroxyl group of glycerol. a third hydroxyl group, which forms an ester with phosphoric acid, which then forms another phosphoester bond with an amino alcohol. Insert picture of glycerophospholipid pg 618

Lecithin and Cephalin Lecithin and cephalin are glycerophospholipids are abundant in brain and nerve tissues. are found in egg yolk, wheat germ, and yeast. contain choline (in lecithins) or either ethanolamine or serine (in cephalins).

Glycerophospholipids Contain Amino Alcohols. Three amino alcohols found in glycerophospholipids are choline, serine, and ethanolamine. In the body, at a physiological pH of 7.4, these amino alcohols are ionized. Insert structures of amino alcohols pg 618 bottom

Glycerophospholipids are Polar and Nonpolar. Glycerophospholipids have both polar and nonpolar regions that allow them to interact with polar and nonpolar substances. an ionized amino alcohol and phosphate portion, called “the head,” which is polar and strongly attracted to water. a hydrocarbon chain known as “the tail,” which is soluble in nonpolar substances.

Formation of Glycerophospholipids The formation of a glycerophospholipid occurs when ester bonds form between glycerol and two fatty acids, and two phosphoester bonds form between phosphoric acid and an ionized amino alcohol and glycerol, such as palmitic acid.

Components of Glycerophospholipids The components of a glycerophospholipid are an amino alcohol (choline here), phosphoric acid, glycerol, and two fatty acids. Insert structure from figure 17.6a

Components of Glycerophospholipids In a glycerophospholipid, a polar “head” contains the ionized amino alcohol and phosphate, while the hydrocarbon chains of two fatty acids make up the nonpolar “tails.” Insert structure from figure 17.6b

Learning Check (let’s do this slowly)… Identify each as a fatty acid, triacylglycerol, amino alcohol or glycerophospholipid. A. glyceryl trioleate B. cephalin C. choline D. palmitic acid

A. glyceryl trioleate triacylglycerol B. cephalin glycerophospholipid Solution Identify each as a fatty acid, triacylglycerol, amino alcohol or glycerophospholipid. A. glyceryl trioleate triacylglycerol B. cephalin glycerophospholipid C. choline amino alcohol D. palmitic acid fatty acid

Learning Check O ║ CH2—O—C— (CH2)16—CH3 + O NH3 ║ │ Which type of glycerophospholipid is this? O ║ CH2—O—C— (CH2)16—CH3 + O NH3 ║ │ CH2—O—P—O—CH2—CH−COO – │ O–

O ║ CH2—O—C— (CH2)16—CH3 + O NH3 ║ │ CH2—O—P—O—CH2—CH−COO – │ O– Note that the “group” on the phosphorous is serine (the amino acid), so this is cephalin!  O ║ CH2—O—C— (CH2)16—CH3 + O NH3 ║ │ CH2—O—P—O—CH2—CH−COO – │ O–

Recognize the following for glycerophospholipids… cephalin Lecithin Can also have serine

Last type of fatty acid lipid… derivatives of sphingosine Sphingosine is an 18-carbon unsaturated amino alcohol. Insert structure top pg 621

Sphingolipids Sphingolipids are phospholipids that contain a long-chain amino alcohol called sphingosine, rather than glycerol.

Sphingomyelins Sphingomyelins, are a group of sphingolipids in which the amine group forms an amide bond to a fatty acid, and the hydroxyl group of sphingosine forms an ester bond with phosphate forming another phosphoester bond to an amino alcohol, such as choline.

Recognize… Sphinghosine a sphinghomylin notice the phosphphate group attached to the top OH Notice the amino alcohol attached to the phosphate group…

Sphingomyelins Sphingomyelins, are abundant in the white matter of the myelin sheath, a coating surrounding the nerve. cells that increase the speed of nerve impulses and insulate and protect the nerve cells.

Multiple Sclerosis In multiple sclerosis, sphingomyelin is lost from the myelin sheath, which protects the neurons in the brain and spinal cord. scars form on the neurons and impair the transmission of nerve signals.

Steroids can begin next lesson…

Summary of Fatty Acid Lipids… Know the five types of fatty acid lipids: Waxes, triglycerides, glycerophospholipids, sphigholipids, and prostoglandins Know the characteristics of fatty acids: # of carbons, saturated, monounsaturated, polyunsaturated, omega 3 vs. omega 6, etc. How do the double bonds affect melting points? Saturated vs. unsaturated

Summary (continued)… Recognize the stereochemistry of the double bonds in unsaturated fatty acids (cis and trans). Be able to rank any fatty acid in terms of melting point (so how do the chain length and saturation affect the melting point)? Know the difference between the simple and mixed triacylglycerols. Know the difference between fats and oils & differentiate between their structures.

Summary (continued)… Know what an essential fatty acid is (and give examples)…these are the omega 3 and omega 6 fatty acids.

Next Lesson… Steroids Reactions of Lipids

A few questions…

Questions… Which has the higher melting point of the structures shown below?

Answer Trans-oleic acid would have a higher melting point than cis because cis cannot “pack” as well…

Identify each type of structure below…

Identify each type of structure below… wax cholesterol prostoglandin phosphoglyceride