Ch. 20 Lipids

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Ch. 20Lipids

• Milbank High School

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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?

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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?

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Lipids

• Fats and oils
• Twice the energy as carbsbut it usually goes
  into storage
• Uses other than energy
• Protection
• Cell membranes
• Fat soluble vitamins A, D, E, and K

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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

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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

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Fatty acids Cont

• 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

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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 25C
• Oils if liquid at same temp

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Fats and Oils Cont

• Saturated fats
• Cholesterol
• Arteriosclerosis
• Use olive oil or canola oil
• They lower LDL cholesterol
• High percentage of monounsaturated fatty acids

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Reactions of Fats and Oils

• Hydrolysis
• Hydrogenation
• Oxidation
• Antioxidants

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Sec. 20.3Soaps

• Saponification
• Second oldest organic synthesis (1st is
  production of ethyl alcohol)
• Hydrolysis of triglycerides sodium carbonate

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How do soaps work?

• Figure 20.4
• Hydrophilic (water soluble)
• Hydrophobic (repelled by water)
• Soaps dont work well in hard water (soap scum)
• Detergent
• Toothpaste!?!

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Sec. 20.4Membrane Lipids

• Phospholipids
• Phosphoglycerides
• Glycolipids
• Sphingolipids
• Sphingomylelins
• Cerebrosides
• Gangliosides

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Sec. 20.5Cell Membranes

• Cytoplasm
• Micelles
• Bilayers
• Three major classes in the membrane bilayer of
  animal cells
• Phospholipids
• Glycolipids
• Cholesterol

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Cell Membranes

• Two rows of phospholipid molecules
• Tail to tail
• Semipermeable
• Integral proteins
• Peripheral Proteins

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Sec. 20.6Steroids Cholesterol and Bile Salts

• Nonsaponifiable
• Bile salts, cholesterol, cortisone (hormone), sex
  hormones, and related compounds
• Must have 4 fused rings

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Cholesterol

• Does not occur in plants
• Most abundant steroid in human body
• Biosynthesis of
• Sex hormones
• Adrenal hormones
• Vitamin D
• Excess cholesterol
• Gall stones

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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

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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

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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

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Cholesterol

• High levels of LDL increase heart disease risk
• High HDL reduces heart risk
• LDLHDL ratio better indicator of heart disease
  risk

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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

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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

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Atherosclerosis

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

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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

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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

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Heart Healthy Foods

• Top 25see article
• Phytoestrogens
• Flaxseed
• Phytosterols
• Carotenoids
• Polyphenols
• Omega-3 fatty acids
• B-Complex vitamins

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Leptin

• Regulates energy intake and enery expenditure
• Appetite and metabolism
• Regulated downward at night by melatonin
• Increased during pregnancy