Ch. 5 Lipids

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University of British Columbia
Food, Nutrition and Health
FNH 250
Gail Hammond

Lipids-organic, insoluble in H2O, 2-24 carbons (18C most common) 1. Triglycerides -made up of 3FAs with a glycerol backbone, 95% of the fat we eat, how fat is stored -1 FA hydrolyzed -> diglyceride (DG) and if 2 FA hydrolyzed -> monoglyceride (MG) Chain Length SCFA=less than 6C (dairy), MCFA=6-12C (coconut oil), LCFA=14-24C (meat) Saturation Saturated FA (SFA) -> cream, coconuttropical oil, chocolate, milk fats MUFA-omega-9 family (double bond 9 Cs from methyl end) -> olive, canola, peanut oil, avocado PUFA-omega-6 family -> corn, soybean, sesame oil and omega-3 -> fish, canola, hemp, flaxseed oil, nut -use ratio of # Cs to # double bonds to name them (eg. 18:1 is monounsaturated 18-C FA) -if unsaturated, either cis (more kinked) or trans (more straight and like saturated fats) -double bonds affected by O2, UV light, chemicals -> rancidity Hydrogenation -prevents rancidity by saturating double bonds, changing cis to trans -saturated fats increase blood cholesterol + risk of heart disease (and trans too, since similar) Essential FAs -dietary fat provides the 2 EFA needed to make compounds 1. Linoleic Acid-omega-6, C18:2; in veggie + seed oils, nuts -helps regulate blood clotting + blood pressure, needed for cell membrane integrity -precursor to arachidonic acid (AA), C20:4 2. Linolenic acid-omega-3, C18:3, in fish, flaxseed, canola oil, soybeans, wheat germ -precursor to EPA + DHA -> used in retina + cerebral cortex, found in human milk, shellfish -AI is ratio of 10:1 for omega 6:3 Function Triglycerides 1. Fuel Source -major E source for muscles at rest + during light activity (to conserve carbs) -enzyme lipase breaks down TG from adipose (low insulin levels-prevents fat breakdown) -> cross adipose cell membrane -> travel thru blood bound to protein albumin to muscle -> when cells need E, break down further (B-oxidation) -> use O2 to make ATP (if more fit, burn more fat bc more O2) -during activity, draw E from blood lipoproteins, adipose, muscle, dietary fat -need CHO to oxidize FA: 2C fat fragments combine with oxaloacetate (made from CHO) in Krebs -> if not enough, left with excess 2-C fats -> body deals with by making ketones 2. Fuel Storage -non bulky storage since TG packed tightly w little water 3. InsulationProtection 4. Structural-myelin sheath, hormones, keep cells fluid + flexible
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