Fatty acid nomenclature Triacylglycerol = TAG = triglyceride Saturated = no C—C double bonds Monounsaturated = one C—C double bond Polyunsaturated = more than one C—C double bond N = omega
Fat chemistry Three fatty acids attached to one glycerol Fatty acids are long chains of COOH.(CH 2 ) n.CH 3 The variation lies in the (CH 2 ) n part Chains with between 2 and 36 C atoms are common, though some microbes can have up to 80
Double bonds in fatty acids Fatty acids containing C—C double bonds are called unsaturated Double bonds are inserted into fatty acid chains by desaturase enzymes The first double bond always goes in between the 8 th and 9 th C, counting from the COOH end Extra double bonds are always separated by at least one single C—C bond Animals can put in extra double bonds only between the first one and the COOH end Plants can also put extra double bonds between the first and the CH 3 end
Shape and function of fatty acids Saturated fatty acids can pack tightly together – They tend to be more solid at room temperature – Examples are butter, lard, suet, wax Unsaturated fatty acids cannot pack so tightly – They tend to be more liquid at room temperature – Examples are margarine, cooking oil, bath oil
How are fatty acids named? C18:0stearic acid C18:1oleic acid C18:2n-6linoleic acid C18:3n-3alpha-linolenic acid C18:1telaidic acid (trans)
Trans fatty acids Made by microbes in the rumen In the cow, most trans fatty acids are oxidised for energy and about 5% are stored Hydrogenation also yields trans fatty acids: 90% of oleic acid is changed into elaidic acid Trans fatty acids have different physical properties and taste from the cis versions Oleic acid is a liquid at room temperature, but elaidic acid is a solid Trans fatty acids are less susceptible to spoilage as enzymes work more slowly on them
Are trans fatty acids harmful? We’ve been eating ruminant-derived trans fatty acids for 9000 years We eat 2-12 g trans fatty acids per day, ~7% total fat intake Diets rich in hydrogenated fats increase this significantly (crisps, fried food, biscuits, pastries, burgers, processed foods) Only 5% of the fatty acids in brain membranes are trans, compared to 14% in adipose tissue Can trans fatty acids be used fast enough to support function?
Conclusions Fats are essential to our well-being Fats and oils consist of long C—C chains with varying numbers of double bonds We can make some fatty acids, but we need more from our diet Trans fatty acids are not harmful in moderation There is a complex fat trafficking system around the body Fatty acids can be used for making membranes and signalling molecules Fat can be used for chemical, mechanical and heat energy Uncoupling protein keeps you warm!