Lipids PDF

Lipids Lipids: important group of chemicals, major in living things Limited solubility in water 1. Fat, oils, and wax containing ester linkage 2. Sterols like cholesterol Fat and Oils - Fat and oil are fatty acid esters of glycerol -...

Lipids Lipids: important group of chemicals, major in living things Limited solubility in water 1. Fat, oils, and wax containing ester linkage 2. Sterols like cholesterol Fat and Oils - Fat and oil are fatty acid esters of glycerol - Important source of energy - Also referred as triglycerides Triglyceride molecule: form by reacting a molecule of glycerol (alcohol) with long chain fatty acids Ex. stearic acid (c17H35COOH) Glycerol (alcohol) +stearic acid (fatty acid) = glyceryl tristearate (triester) + water Stearic acid: has only single carbon-carbon bonds in molecule - Saturated Ex. beefsteak has high glyceryl stearate content, saturated fat Carbon - carbon double bonds are present in fatty acid, unsaturated Ex. olive oil, mixture of glycerol fatty acid esters, on digestion, unsaturated fatty acids (ex. Oleic, linoleic, linolenic) Oleic acid: - Similar to stearic acid structure - difference: presence of one carbon- carbon double bond in chain = monounsaturated fatty acid. Ex. olive oil and avocado oil Double bond is 9 carbons from terminal CH3 or methyl group, acid is omega nine monounsaturated fatty acid. Linoleic(omega 6) and linolenic (omega 3) fatty acids: - Since they have more than one carbon - carbon double bond = polyunsaturated Ex. - nuts and veggi oil (linoleic) - Flaxseeds and chia seeds (linolenic) Body can synthesize saturated and monounsaturated fatty acids, it cannot produce omega 3 and 6 (essential fatty acid) - Required for the construction of cell membranes, precursors for hormone production FACT: low fat diet, most fat from polyunsaturated fat (ex. Olive oil and oily fish) is healthy - Ratio: omega 3 and 6 less than 1:10. Trans Fatty Acid Naturally occurring lipids (fat and oil) - altered (hydrogenation) - Adding hydrogen to the unsaturated fat (oils and fats) Process: some double bonds present in polyunsaturated fatty acids are removed. - Polyunsaturated fatty acids have double bonds, creates kinks in the chain, making it healthier - Adding hydrogen removes the double bonds, converting to single bonds=trans fat - Higher melting point Naturally occuring = ‘cis’ configuration Process changes configuration of remaining double bonds, turning ‘cis’ - ‘trans’ configuration - ‘Trans’ fatty acid behaves biologically like saturated fatty acids - Manufactured foods using hydrogenated oils alter balance of saturated to unsaturated fatty acids = NEGATIVE.  Cholesterol: Sterols are another type of lipids - Atoms of carbon, hydrogen and oxygen arranged in four fused rings with a range of side chains. - cholesterol is main sterol found in animal origins - Structural role in cell membranes and body - steroid hormones, vitamine D and bile acids - cholesterol in food has fatty acid attach = cholesterol ester - liver makes over half cholesterol needed, other is diet Molecules (lipoprotein) transport cholesterol around bloodstream, - Carriers lipoproteins: 1. Low density lipoprotein (LDL) 2. High density lipoprotein (HDL) LDL major carrier of cholesterol from liver to rest of body - Eating more saturated fat elevates LDL HDL mops up cholesterol from the bloodstream, takes back to the liver, lessening deposit in arteries. - Higher ratio of HDL lowers risk of artery disease