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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