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Lipids

Lipids. B.4. 3 Main Types of Lipids (B.4.1…). ‘lipid’ comes from lipos , the Greek word for fat all are hydrophobic (water-fearing/insoluble in water) greasy, oily. 1. Triglycerides (fats and oils) found in adipocyte cells that are in fatty tissue

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Lipids

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  1. Lipids B.4

  2. 3 Main Types of Lipids (B.4.1…)

  3. ‘lipid’ comes from lipos, the Greek word for fat • all are hydrophobic (water-fearing/insoluble in water) • greasy, oily

  4. 1. Triglycerides (fats and oils) • found in adipocyte cells that are in fatty tissue • condensation reactions cause 3 fatty acidschains (16-22 carbon atoms) to covalently bond to a molecule of glycerol (B.4.6) • produces 3 molecules of water • this bond between a carboxyl group (on the fatty acid) and an hydroxyl group (on the glycerol) is called an ester linkage

  5. the fatty acids found in triglycerides (and other lipids) are either: (B.4.3) • saturated fat • do NOT contain C=C bonds • therefore straight chained and have high melting points • lard and butter • unsaturated fat • have double bonds between one (monounsaturated fats) or more (polyunsaturated fats) of the carbons in the chain • causes a kink in the carbon chain which prevents them from packing close together and therefore have low melting points (Van der Wall’s forces are weaker) • vegetable oils

  6. Saturated vs. Unsaturated fatty acids (2:51)

  7. Common Fatty Acids 10

  8. Iodine number and C=C bonds (B.4.5) • the addition of iodine is used to determine the # of C=C bonds • iodine causes the double bonds to break and form single bonds • one mole of C=C requires one mole of I2to react • iodine is purple • as iodine is added to unsat fat, the purple color disappears as the addition reaction takes place • iodine index is the # of grams of iodine that reacts with 100 g of unsatfat 1 1

  9. Iodine Index of Common Fats/ Oils

  10. Example problem • 0.010 mol of linoleic acid (C18H32O2) reacts with 5.1 g of iodine. Determine the number of double bonds present in linoleic acid. 5.1 g I2 1 mol I2 254 g I2 • therefore, 0.010 mol of linoleic acid reacts with 0.020 mol of I2 • 1:2 ratio • linoleic acid must have two double bonds = 0.020 mol I2 X

  11. Compare essential fatty acids and state their importance (B.4.4) • primary structural components of cell membranes • essential fatty acids are those that the body cannot synthesize on its own • must be acquired from the foods we eat • these are linoleic (omega-6 fatty acid) and linolenic (omega-3-fatty acid) • important… • precursors for larger fatty acids • promote healthy immune system • maintain healthy cholesterol levels 15

  12. Compare omega-3 and omega-6 fatty acids

  13. omega-6 linoleic acid • obtained from seeds and vegetables • the omega-6 indicates that there is a C=C on the 6th carbon from the end of the carbon chain 17

  14. omega-3 linolenicacid • obtained from green leaves • the omega-3 indicates that there is a C=C on the 3rd carbon from the end of the carbon chain

  15. Hydrolysis of triglycerides (B.4.7) • the splitting of covalent bonds using water • the reverse of making triglycerides • digestion splits fat into carboxylic acids and glycerol • the enzyme lipase is necessary

  16. 2. Phospholipids • major structural components of cell membranes • like triglycerides, but one of the fatty acids is replaced by a phosphate group that is negative and a nitrogen group that is postive • this caused the “heads” to love water (hydrophilic) • the uncharged “tails” avoid water (hydrophobic) _ +

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  20. 3. Steroids • cholesterol is the most abundant and important steroid • maintains fluidity in cell membranes • the precursor of other important steroids • can contribute to heart disease • structurally diff. from other lipids • contain four interlocking rings of carbon and hydrogen

  21. lipoproteins • molecules made of proteins and fat • transportcholesterol around the body (B.4.2) • low density lipoproteins (LDL) “bad cholesterol” • transport cholesterol to cells to be used • however, can build up and cause cardiovascular disease • high density lipoproteins (HDL) “good cholesterol” • doesn’t have much cholesterol, therefore, can abosrb more cholesterol from the arteries and transports it back to the liver

  22. Lipids important roles and negative effects on health (B.4.9) • important roles: • energy storage- fat in humans • fats provide our most concentrated form of energy with 37 kJ/gram vs. carbohydrates with 16 kJ/gram • have less oxygen than carbs • therefore, more oxidation can take place which releases more energy • insulation and protection • structural component of cell membranes • negative effects • increased risk of heart disease from elevated LDL’s • obesity

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