Ch. 5 Lipids

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26 Sep 2011
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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, coconut/tropical 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 b/c 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 Kreb’s -> 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. Insulation/Protection
4. Structural-myelin sheath, hormones, keep cells fluid + flexible
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