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Lipids

Lipids. Lipids. long-term energy storage do not consist of polymers insoluble in polar substances structural components of cells – ex. phospholipids are the major building block in cell membranes "messengers" (hormones) . Lipid Construction.

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Lipids

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  1. Lipids

  2. Lipids • long-term energy storage • do not consist of polymers • insoluble in polar substances • structural components of cells – ex. phospholipids are the major building block in cell membranes • "messengers" (hormones)

  3. Lipid Construction • Lipids are composed of three fatty acids covalently bonded to a 3-carbon glycerol • The fatty acids are composed of CH2 units, and are hydrophobic/not water soluble

  4. C C C C C C C H C H O H C C C C C C C C C HO H H H H H H H H H H H H H H H H C OH Fatty acid (palmitic acid) H C OH H Glycerol (a) Dehydration reaction in the synthesis of a fat Ester linkage O H H H H H H H H H H H H H H H H H H O C C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H O H H H H H H H H H H H H H H H O C H C C C C C C C H C C C C C C C C C H H H H H H H H H H H H H H H O H H H H H H H H H H H H H H H H H C O C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H H Fats • Fats • Are constructed from two types of smaller molecules, a single glycerol and usually three fatty acids H H H H H H H H O H H H H H H H H Figure 5.11 (b) Fat molecule (triacylglycerol)

  5. Stearic acid Figure 5.12 (a) Saturated fat and fatty acid • Saturated fatty acids • Have the maximum number of hydrogen atoms possible • Have no double bonds

  6. Saturated Fats

  7. Oleic acid cis double bond causes bending Figure 5.12 (b) Unsaturated fat and fatty acid • Unsaturated fatty acids • Have one or more double bonds

  8. Unsaturated Fat

  9. Saturated refers to the "saturation" of the molecule by hydrogen atoms • The presence of a double C=C covalent bond reduces the number of hydrogens that can bond to the carbon chain, hence the application of the term "unsaturated“. • Fatty acids can be saturated (meaning they have as many hydrogens bonded to their carbons as possible) or unsaturated (with one or more double bonds connecting their carbons, hence fewer hydrogens). • Fat - solid at room temperature (saturated) • Oil - liquid (unsaturated)

  10. Phospholipids • Phospholipids • Have only two fatty acids • Have a phosphate group instead of a third fatty acid

  11. + CH2 Choline N(CH3)3 CH2 O Phosphate Hydrophilic head – P O O O CH2 CH CH2 Glycerol O O C O C O Fatty acids Hydrophilic head Hydrophobic tails Hydrophobic tails (c) Phospholipid symbol (b) Space-filling model Figure 5.13 (a) Structural formula • Phospholipid structure • Consists of a hydrophilic “head” and hydrophobic “tails”

  12. WATER Hydrophilic head WATER Hydrophobic tail Figure 5.14 • The structure of phospholipids • Results in a bilayer arrangement found in cell membranes

  13. H3C CH3 CH3 CH3 CH3 HO Figure 5.15 Cholesterol and steroids • Steroids - lipids characterized by a carbon skeleton consisting of four fused rings

  14. H3C CH3 CH3 CH3 CH3 HO Figure 5.15 • One steroid, cholesterol • Is found in cell membranes • Is a precursor for some hormones

  15. Cholesterol • Excess cholesterol in the blood has been linked to atherosclerosis, hardening of the arteries.

  16. Functions of Fats and Oils • Long term energy storage • Animals convert excess sugars (beyond their glycogen storage capacities) into fats • Plants store excess sugars as starch, although some seeds and fruits have energy stored as oils - corn oil, peanut oil, palm oil, canola oil, and sunflower oil • Fats store six times as much energy as glycogen.

  17. Insulation - heat retention • Cushion – protection (body organs, fetus) • Structural components of cells - Phospholipids and glycolipids – cell membranes • Phospholipids are modified so that a phosphate group (PO4-) is added to one of the fatty acids. • The addition of this group makes a polar "head" and two nonpolar "tails". • Waxes – cuticle -waxy layer covering the leaves and stems of many land plants; and protective coverings on skin and fur of animals • Hormones – body regulation

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