NUTR 3000 - Lipids and Fatty Acids

Properties of fatty acids

-hydrophobic

-capable of storing high chemical energy (lots of calories)

-electronic insulators

Classifications of lipids

Simple lipids

-fats, oils, waxes

Compound lipids

-phospholipids, glycolipids, glycoproteins

Derived lipids

-fatty acids, glycerol,

Sterols

-steroid alcohol, cholesterol

Terpenes

0resin and turpentine

Purpose of lipids

energy storage

source of essential fatty FA

carrier of fat soluble vitamins

structural (membranes)

Fatty acid structure is similar to

gasoline and other mineral oils

Fats are easily stored and carried around since it is

lightweight and compact

saturated vs unsaturated

saturated = no DB

Fatty Acid notation

# carbons : # double bonds-number of carbon atoms between methyl terminal and DB

ex: 18:2n-6

Can all FAs be synthesized by animal tissues

no, and not in significant ammount

Essential FAs must be supplied by

diet

non-essential AA's can be produced through

de novo synthesis using carb precursors (glucose and lactate) and AA precursors

biological uses of unsaturated membranes

-adjust the fluidity of membranes

-increase the front resistance of plants

-waterproof feathering

-act as signalling molecules

Saturated FAs are undesirable because

DBs are reactive by oxidation reactions, dangerous for fireworks

Fat soluble vitamins are

ADEK

Toxicity of too many stored fat soluble vitamins in the body is

hypervitaminosis

A deficiency in fat soluble vitamins caused by

low fat intake or impaired absorbtion

fats don't form polymers, they cluster, forming

bilayers ( phospholipids found in all except archaea)

When fat is catabolyzed it is released into the bloodstream from

adipocytes

when fat is catabolized it is released into the bloodstream as

FFAs (free fatty acids) and glycerol

Why is glycerol transported easily

because it is water soluble

FAs in the blood are taken up by

muscles and tissues

FAs are oxidized in the

mitochondria

white fat stores

triglycerides and releases when needed elsewhere

brown fat stores

triglyceride and oxides them when needed to produce heat

young animals without brown fat have trouble regulating heat

Brown fat is present in

humans, sheep, etc., but absent in birds and pigs

brown fat oxidizes fat to produce heat by

not producing ATP at the end of the pathway, rather heat.

why is brown fat called brown

It uses an uncoupling protein indicative of brown tissue

Do plants have brown fat?

yes, some generate heat to release volatiles during flowering and fruiting

In animals, brown fat is important for

-non-shivering thermogenesis in newborns and cold-adapted adults

-diet-induced thermogenesis to burn excess calories if diet is calorically deficient (basis of Atkins fad diet)

The main energy source of ruminants are

VFAs

VFAs are produced in the rumen via

fermentation

the main energy source of ruminants are

VFAs

VFA's include

acetate, propionate, butyrate

VFAs are absorbed through the __________________ and carried from ruminal veins to the ....

rumen epithelium

portal vein in the liver

microbes of the rumen ______________ fatty acids

hydrogenate (saturate unsaturated VFAs)

for example, they will form stearic acid (C18:0 from C18:1)

The saturation of VFAs is affected by the environment, for example

large amounts of linoleic acid will stop saturation

saturation an be stopped by rumen-protecting FAs by encapsulating oils

Polyunsaturated fatty acids will bypass the rumen, be digested in SI, and be incorporated in

plasma, milk, and depot fats.

you may want to do this because poly unsaturated fatty acids (PUFA) in cows fed rumen-protected fat is 20-30%, where normal is 2-3%. This can tap into a market for omega 3 milk products

two types of rancidity of fatty acids

hydrolytic

-triglyceride fatty acids split from glycerol

oxidative

-free radical formation

hydrolytic rancidity can be due to

-lipase (produced by bacteria and mold, contamination)

-mono and diglycerides and free fatty acids

-releasing FFAs alters colour and odour and flavour

-gives something like rancid butter (butyric acid)

oxidative rancidity is due to

the destruction of essential FAs from temp, moisture, light or oxygen (poor storage). This causes a hydrogen atom to be released, forming a peroxide (a double bond shifts and a free radical joins with oxygen).

The peroxide then joins with the released hydrogen to form a hydroperoxide.

hydroperoxides can polymerize with each other to form a

film, as in linseed oil paint

hydroperoxides can also break down into

aldehydes and ketones which emit odor

what type of rancidity is autocatalytic

oxidative

autocatalytic rancidity means that

once it starts, it gets faster and faster.

autocatalytic rancidity can be ___________ with ____________but it cant be _____________

stopped or slowed with antioxidants (vitamin E), but t cant be reversed

how do antioxidants stop the reaction

by replacing the missing hydrogen

Examples of polyunsaturated FAs

Linolenic Acid

18:3n-3

DHA (Docosahexaenoic acid)

22:6n-3

EPA (Eicosapentaenoic acid)

20:5n-3