Ch. 20Lipids

Milbank High School

Objectives

• 1.How are lipids defined? How are they classified?• 2.What is a fatty acid? What is the difference between a

saturated, monounsaturated, and polyunsaturated fatty acid?

• 3.Why are fats and oils referred to as triglycerides (or triacylglycerols)? What determines if a triglyceride is a fat or oil?

• 4.What does the iodine number tell you about a triglyceride?

• 5.Why is it important for a soap to have both a hydrophilic and a hydrophobic end?

Objectives

• 6.What are the functions of phospholipids, glycolipids, and sphingolipids? What distinguishing characteristics are used to place lipids into one of these categories?

• 7.What are the major components of cell membranes and how are they arranged?

• 8.What are the functions of steroids?• 9.What is the link between cholesterol,

lipoproteins, and cardiovascular disease?

Lipids

• Fats and oils

• Twice the energy as carbs…but it usually goes into storage

• Uses other than energy:– Protection– Cell membranes– Fat soluble vitamins A, D, E, and K

Lipids

• Classified as a group based upon their solubility– INSOLUBLE in water

• Lipid: compound isolated from body tissues that is more soluble in organic solvents than in water

• Broad variations in structure

Sec. 20.1Fatty Acids

• Carboxylic acids – Components of fats and oils

• Even number of carbon atoms

• Saturated fatty acids

• Monounsaturated fatty acids

• Polyunsaturated fatty acids

                   

        

Fatty acids Con’t• Use table 20.1 to answer the following

questions:– Find an example of a:

• Saturated fatty acid• Polyunsaturated fatty acid• Monounsaturated fatty acid

– Draw• Myristic acid• Oleic acid• Linoleic acid

Sec. 20.2Fats and Oils

• Most abundant lipids in nature

• Energy, protection, insulators

• “Triglycerides”– Esters composed of three fatty acids joined

to glycerol, a trihydroxy alcohol– Fats if solid at 25°C– Oils if liquid at same temp

                                                                                                       

          

Fats and Oils Con’t• Saturated fats

– Cholesterol– Arteriosclerosis

• Use olive oil or canola oil– They lower LDL cholesterol– High percentage of monounsaturated fatty

acids

Reactions of Fats and Oils

• Hydrolysis

• Hydrogenation • Oxidation• Antioxidants

                                                                                                                                     

                                     

Sec. 20.3Soaps

• Saponification

• Second oldest organic synthesis (1st is production of ethyl alcohol)

• Hydrolysis of triglycerides + sodium carbonate

How do soaps work?

• Figure 20.4

• Hydrophilic (water soluble)

• Hydrophobic (repelled by water)

• Soaps don’t work well in hard water (soap scum)

• Detergent – Toothpaste!?!

Sec. 20.4Membrane Lipids

• Phospholipids– Phosphoglycerides

• Glycolipids• Sphingolipids• Sphingomylelins

– Cerebrosides– Gangliosides

Sec. 20.5Cell Membranes

• Cytoplasm• Micelles• Bilayers• Three major classes in the membrane

bilayer of animal cells:– Phospholipids– Glycolipids– Cholesterol

Cell Membranes

• Two rows of phospholipid molecules– Tail to tail

• Semipermeable

• Integral proteins

• Peripheral Proteins

Sec. 20.6Steroids: Cholesterol and Bile

Salts

• Nonsaponifiable• Bile salts, cholesterol, cortisone

(hormone), sex hormones, and related compounds

• Must have 4 fused rings

Cholesterol

• Does not occur in plants• Most abundant steroid in human body• Biosynthesis of:

– Sex hormones– Adrenal hormones– Vitamin D

• Excess cholesterol– Gall stones

Bile

• Produced in liver

• Bile salts– Aid in the digestion of dietary lipids– Aid in absorption of fatty acids, cholesterol,

and fat-soluble vitamins

• Effective detergents and emulsifying agents

Sec. 20.7 Cholesterol and Cardiovascular

Disease• Primary factor in atherosclerosis,

coronary artery disease, and stroke– 41.5% of deaths nationwide– High cholesterol (over 260mg/100mL)– Males higher than females

Cholesterol

• Not soluble in water• Cannot be transported in blood unless linked

with a lipoprotein (water-soluble proteins)• 4 types

– Chylomicrons– Very low density (VLDL)– Low-density proteins (LDL)– High-density proteins (HDL)

• Contains least amount of lipid

Cholesterol

• High levels of LDL increase heart disease risk

• High HDL reduces heart risk– LDL:HDL ratio better indicator of heart

disease risk

HDL

• Transport excess cholesterol from various tissues to the liver where it is metabolized

• Basically they are removing cholesterol from the blood

• Increase HDL by:– Exercise– Lose weight– Alcohol in moderation

Dietary Modifications

• Average American: 600 mg/day of cholesterol– Recommended: 300 mg/day– One large egg: 215 mg

• Integrate unsaturated fat for saturated fats– Omega-3 fatty acids– Fish oil– Reason?

• Polyunsaturated fatty acids

Atherosclerosis

• Most common form of arteriosclerosis (thickening of the arterial walls)

• LDL’s lodge in arteries, oxidized, white blood cells try to consume oxidized products, enlarged white blood cells accumulate, causes plaque that narrows arteries

• Most serious consequence: heart attack

Statins

• Inhibits the enzyme HMG-CoA reductase • Inhibition of this enzyme in the liver stimulates

LDL receptors, resulting in an increased clearance of low-density lipoprotein (LDL) from the bloodstream and a decrease in blood cholesterol levels.

• Lipitor, Crestor

Olestra

• Fat substitute, calorie free• Synthesized using a sucrose molecole, which

holds many fatty acids chains• Molecule is too large to move through

intestinal wall• Olean• May cause cramps and diarrhea

Heart Healthy Foods

• Top 25—see article• Phytoestrogens

– Flaxseed

• Phytosterols• Carotenoids• Polyphenols• Omega-3 fatty acids• B-Complex vitamins

Leptin

• Regulates energy intake and enery expenditure– Appetite and metabolism

• Regulated downward at night by melatonin

• Increased during pregnancy