Goals of the Day… Finish lipids if we didn’t finish it last lesson…(sphingolipids specifically) Steroids Reactions of Triacylglycerides

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

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… The other type of lipid is a steroid. These have a base unit of four rings attached to each other… Examples are: choloesterol, testosterone & estrogen.

Steroid Nucleus Steroid molecules contain a steroid nucleus with 3 cyclohexane rings, 1 cyclopentane ring, no fatty acids, and a total of four rings A, B, C, D. The steroid nucleus is numbered from the carbon atoms in ring A to two methyl groups at 18 and 19.

Cholesterol is the most important and abundant steroid in the body. is a sterol because it contains an oxygen atom as a hydroxyl group, –OH on carbon 3. has a double bond between carbon 5 and carbon 6. has methyl –CH 3 groups, at carbon 10 and 13. has a carbon chain at carbon 17.

Cholesterol Cholesterol is a component of cellular membranes, myelin sheaths, and brain and nerve tissues.

Cholesterol in the Body Cholesterol in the body is obtained from meats, milk, and eggs and synthesized in the liver. clogs arteries when high levels form plaque. A normal, open artery. An artery clogged by cholesterol plaque

Cholesterol in Foods A typical American diet includes 400–500 mg of cholesterol per day. The American Heart Association has recommended no more than 300 mg of cholesterol per day. Saturated fats in the diet may stimulate the production of cholesterol by the liver.

Learning Check Match the components of the cholesterol molecule with each of the following: alkyl chain hydroxyl group steroid nucleus methyl group A C B D

Solution Match the components of the cholesterol molecule with each of the following: alkyl chain hydroxyl group steroid nucleus methyl group A C B D D A C B

Bile Salts Bile salts are synthesized from cholesterol in the liver. are stored in the gallbladder and secreted into the small intestine. have a polar and a nonpolar region. help in the absorption of cholesterol into the intestinal mucosa.

Sodium Glycocholate, a Bile Salt Nonpolar region Polar region

Gallstones Gallstones are formed when large amounts of cholesterol accumulate in the gallbladder. composed of almost 100% cholesterol, with some calcium salts, fatty acids, and glycerophospholipids.

Lipoproteins combine lipids with proteins and phospholipids. are soluble in water because the surface consists of polar lipids.

Lipoprotein… Phospholipids & proteins on the outside (polar) Cholesterol & triglycerides on the inside (nonpolar)

Lipoproteins (HDL, LDL, & VDLs) A spherical lipoprotein particle surrounds nonpolar lipids with polar lipids and protein for transport to body cells.

Types of Lipoproteins Lipoproteins differ in density, composition, and function and include: chylomicrons, very low-density lipoprotein (VLDLs); low-density lipoproteins (LDLs), which carry cholesterol to the tissues; and high-density lipoproteins (HDLs) that pick up cholesterol from the tissues and carry it to the liver.

HDLs are more dense than LDLs due to the increased amount of protein present. pick up cholesterol from the tissues and carry it to the liver, where it can be converted to bile salts, which are eliminated from the body, are called “good” cholesterol.

LDLs transport cholesterol to tissues where it can be used for synthesis of cell membranes and steroid hormones. deposit cholesterol in the arteries in the form of plaque when cholesterol levels exceed levels needed by tissues. called “bad” cholesterol for their contribution to heart disease.

VLDLs VLDLs carry the triacylglycerols synthesized in the liver to the adipose tissues for storage. Insert fig pg 626

Summary… HDLs help get rid of cholesterol LDLs take cholesterol to the tissues (so it’s bad)

Lipid Panel A lipid panel is a blood test that measures serum lipid levels including: cholesterol triglycerides high-density lipoprotein (HDL) low-density lipoprotein (LDL) The results of a lipid panel are used to evaluate a patient’s risk of heart disease.

Lipid Panel Levels…

Lipid Bilayer of Cell Membranes… The outer layer of cell membranes is hydrophilic while the inner Part is hydrophobic…

Steroid Hormones Steroid hormones are chemical messengers in cells. are produced from cholesterol. include sex hormones, such as androgens (testosterone) in males and estrogens (estradiol) in females.

Steroid Hormones

Adrenal Corticosteroids (FYI) Adrenal corticosteroids are steroid hormones produced by the adrenal glands located on the top of each kidney and include: aldosterone, which regulates electrolytes and water balance by the kidneys; cortisol, released under stress to increase blood sugar and regulate carbohydrate, fat, and protein metabolism; and prednisone, a synthetic corticosteroid, derived from cortisone, used for reducing inflammation, treating asthma and rheumatoid arthritis.

Adrenal Corticosteroids (recognize they are steroids)

Learning Check Identify each of the following as a steroid, triacylglycerol, phospholipid, or sphingolipid. A. cholesterol B. glycerol, 2 fatty acids, phosphate, and choline C. glyceryl tristearate D. sphingosine, fatty acid, phosphate, and choline E. estradiol F. bile salts G. lipids in plasma membranes

Solution A. cholesterol steroid B. glycerol, 2 fatty acids,phospholipid phosphate, and choline C. glyceryl tristearate triacylglycerol D. sphingosine, fatty acid, sphingolipid phosphate, and choline E. estradiolsteroid F. bile salts steroid G. lipids in plasma phospholipid membranes sphingolipid

Five types of fatty acid lipids: Waxes triglycerides glycerophospholipids prostoglandins Steroids: sphingomyein

Four Reactions… The chemical reactions of triacylglycerols are similar to those of alkenes and esters. esterification (making an ester) ester hydrolysis (adding water to the ester to get the carboxylic acid & alcohol) Saponification (adding NaOH and making a salt) hydrogenation (adding H2 to the double bonds)

Four Reactions The chemical reactions of triacylglycerols are similar to those of alkenes and esters. esterification (making the three esters of the triacylglycerol) ester hydrolysis (breaking the triacylglycerol into its three fatty acids and glycerol) Saponification (adding NaOH and making a salt) hydrogenation (adding H2 to the double bonds)

Esterification… To form the triacylglycerols, you take 3 fatty acids and glycerol…so you make 3 ester bonds!

Hydrolysis In acid or enzyme hydrolysis, water adds to the ester bonds. a strong acid, such as HCl or H 2 SO 4, or an enzyme catalyst is required.

Hydrolysis of a Triacylglycerol… In acid or enzyme hydrolysis, water adds to the ester bonds. triacylglycerols hydrolyze forming glycerol and three fatty acids. a strong acid, such as HCl or H 2 SO 4, or an enzyme catalyst is required.

Base Hydrolysis (Saponification ) In base hydrolysis (saponification),

Base Hydrolysis (Saponification ) In base hydrolysis (saponification) of a triacylglycerol… a triacylglycerol reacts with heat and a strong base. a triacylglycerol splits into glycerol and the salts of fatty acids (soap). a solid soap that can be molded into a desired shape is produced when NaOH is used. a softer, liquid soap is produced when KOH is used. polyunsaturated oils produce softer soaps.

Saponification glycerol + salts of fatty acids (soap) Fat or oil + strong base

Recall the following... In hydrogenation, double bonds in unsaturated fatty acids react with H 2 in the presence of a Ni or Pt catalyst. Reduction of the double bonds…

Hydrogenation of Glyceryl Trioleate In a hydrogenation reaction, H 2 adds across the double bond to form a carbon–carbon single bond.

Learning Check Draw (explain) the condensed structural formula of the product of the following reaction.

Solution

Hydrogenation of Oils The hydrogenation of oils converts double bonds to single bonds, adds hydrogen (H 2 ) to the carbon atoms of double bonds, increases the melting point, and produces solids, such as margarine and shortening

Olestra, a Fat Substitute Olestra is used in foods as an artificial fat. composed of 6–8 long-chain fatty acids attached by ester links to a sucrose (not glycerol) molecule. not broken down in the intestinal tract.

Unsaturated fatty acids can be cis with bulky groups on the same side of, or trans with bulky groups on opposite sides of. Cis and Trans Fatty Acids

Trans Fatty Acids and Hydrogenation Trans fatty acids are formed during hydrogenation when cis double bonds are converted to an undesirable side product with a trans double bond. in the body behave like saturated fatty acids. are estimated to make up 2–4% of our total calories. The American Heart Association recommends the use of soft margarine, which is only slightly hydrogenated and therefore has fewer trans fatty acids.

Trans Fats In vegetable oils, the unsaturated fats usually contain cis double bonds. during hydrogenation, some cis double bonds are converted to trans double bonds (more stable), causing a change in the fatty acid structure.

Formation of Trans Fats

Learning Check Identify each statement as true (T) or false (F). 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.

Solution Identify each statement as true (T) or false (F). T A. There are more unsaturated fats in vegetable oils. F B. Vegetable oils have higher melting points than fats. T C. Hydrogenation of oils converts some cis-double bonds to trans-double bonds. T D. Animal fats have more saturated fats.

Summary of Organic and Lipid Reactions

Lipid Summary (types of lipids) Given the structure of a lipid, classify it according to type (fat, oil, wax, prostaglandin, glycerophospohlipid, sphingolipid, or steroid). Recognize a steroid base structure (esterogen, bile salts, cholesterol, etc.) What is the classification of the structure shown?

This is a prostoglandin…

Summary (reactions)… Reactions of triglycerides (H2 addition, H2O addition, saponification, and forming triglycerides). Partial hydrogenation of oils & what it has to do with trans fats. How many acids are formed when a triacylglycerol is hydrolyzed with acid in water?

3 acids form… How many acids are formed when a triacylglycerol is hydrolyzed with acid in water? Remember that with the triacylglycerols, the reactions (except for H2 addition) usually occur in sets of 3 because of the glycerol’s 3 OH groups!

Summary (functions)… Know the major uses of cholesterol in the body. (helps maintain cell membrane structure)… Know how lipids are transported through the body. (VDLs, LDLs, and HDLs)

Summary (functions)… Describe the lipid bilayer model of cell membranes. Know what a micelle looks like, and how it helps clean.

Summary (continued)… State the function of bile salts in the intestines. Help form the micelles…

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…

What happens in the following reaction?

The hydrogens will add to the double bond of the chain…

Identify each type of structure below…

cholesterol wax prostoglandin phosphoglyceride

What you need to know …

Schedule for the next few weeks… MondayWednesday 27 finish lipids (rxns)& a little Amines & amides29 online lesson Nov 3 reviewNov 5 th exam 3 Bring PE3 & worksheet 3 Thursday, October 30 th, 11:30-1:00 CN-quad (Halloween activity)! Extra credit for helping!

What happens in the following reaction?

The hydrogens will add to the double bond of the chain…

Passive Transport, Facilitated Transport & Active Transport….

Passive Transport

Active Transport Moves from low concentration to high concetration (requires energy)

Facilitated Transport