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LIPIDS C, H, O © 2016 Paul Billiet ODWS
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Lipids More hydrogen (more reduced) than carbohydrates
Insoluble in water, soluble in organic solvents (alcohols, acetone, chloroform etc). © 2016 Paul Billiet ODWS
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Fatty acids: carboxylic acid + long hydrocarbon chain
OH CH3 Carboxylic acid Hydrocarbon chain A saturated fatty acid An unsaturated fatty acid C O OH CH3 © 2016 Paul Billiet ODWS
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Unsaturated fatty acids
no double bonds one or more double bonds abundant in fats abundant in oils more reduced less reduced more energy less energy high melting point low melting point © 2016 Paul Billiet ODWS
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Cis and Trans Fatty Acids
© 2016 Paul Billiet ODWS
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Cis & trans fats compared
Cis fat Trans fat Occurance Natural Some in meat & dairy products but mostly from processed foods e.g. margerine Characteristics Lower melting point. Molecule bent Higher melting point Molecule straight Health effects Generally good Bad for plaque build up CVD Lowers HDLs and raises LDLs © 2016 Paul Billiet ODWS
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High and Low Density Lipoproteins
HDL LDL Effect Encourages the transport of cholesterol and fats to the liver for excretion or re-use. Encourages the accumulation of cholesterol in tissues and arteries. Leads to build up of plaque and atheromes CVD Diet HDL tend to increase where diets are rich in omega-3 fatty acids, polyunsatyrated fatty acids, and fibre LDLs tend to increase where diets are rich in trans fats, refined carbohydrates, cholesterol and saturated fatty acids “Good cholesterol” “Bad cholesterol” © 2016 Paul Billiet ODWS
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Fats and Oils fatty acids + glycerol (1, 2 or 3 = mono , di or triglycerides) C O OH CH3 HO – CH2 HO - CH2 HO - CH C O OH CH3 Condensation reactions © 2016 Paul Billiet ODWS
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Two fatty acids joining glycerol = A diglyceride
CH3 O – CH2 HO – CH2 O - CH + 2H20 © 2016 Paul Billiet ODWS
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Phospholipids in lipoprotein membranes (plasma, nuclear, mitochondrial etc.) C O CH3 O – CH2 CH2 – O – HPO3- O – CH Phosphate group © 2016 Paul Billiet ODWS
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Other lipids Steroids: multiple ring structures (e.g. cholesterol)
Functions: cell membrane structure, digestion (help to emulsify fats), hormones (testosterone etc), vitamins (e.g. Vitamin D), poisons Waxes: long chain alcohol + fatty acids Water proof coating to leaves, fur, feathers, insect exoskeletons. Used by bees to construct their honey combs. © 2016 Paul Billiet ODWS
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LIPID FUNCTIONS IN GENERAL
STRUCTURAL: biological membranes (phospholipids, steroids, glycolipids), cushioning (fat deposits round the kidneys) ELECTRICAL INSULATION: myelin sheath round axons THERMAL INSULATION: subcutaneous fat deposits WATER PROOFING: waxes and oils ENERGY STORE AND SUBSTRATE: very condensed form of energy (37 kJ g-1) used by animals and seeds HORMONES: steroids VITAMINS: precursor to Vit D BUOYANCY: oil droplets in plankton. © 2016 Paul Billiet ODWS
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