LIPIDS

General: organic compounds that contain C, H, O

Carbohydrates = CH2O

Lipids = more reduced = more H, less O2

More reduced = more energy dense: 2.25 X more (9/4=2.25)

Most feeds contain less than 5% fat

Humans = ~18% fat : 18X 2.25 = 40% calories from fat.

* Ideal = < 30% calories should come from fat, animals not a problem, low fat diet anyhow.

Structure:

CH3(CH2)X-COOH

Non-polar, H3O insoluble

Carboxylic acid = polar, H3O soluble

Short chain: less than 14 carbons

2

acetate

CH3COOH

3

propionate

CH3CH2COOH

4

butyrate

CH3(CH2)2COOH = CH3CH2 CH2COOH

 

Medium and long chain:

Almost all have even number of carbons

Most fatty acids are long chain

Saturated FA: No double bond C (no p bonds) General formula = CH3(CH2)XCOOH

myristate

C14:0

palmitate

C16:0

stearate

C18:0

 

Unsaturated FA: p bonds

palmitoleic

C16:1

oleic

C18:1

linoleic

C18:2

linolenic

C18:3

arachidonic

C20:4

 

Essential FA:

Can not be synthesized by the body, therefore dietary requirement

linoleic

linolenic

arachidonic (the cat can not synthesize)

Dietary From:

Triglyceride (TG): glycerol + 3 fatty acids

Di-: glycerol + 2 fatty acids

Mono-: glycerol + 1 fatty acid

Phospho-: glyceride + 2 fatty acids + phosphate

Glyco-: CHO group

Sulfo-: SO4

Lipoprotein: contains protein

1. low density lipoprotein (LDL) = ­ lipid, ¯ protein (bad cholesterol)

2. high density lipoprotein (HDL) = ¯ lipid, ­ protein (good cholesterol)

Other Lipds

Waxes: esters of fatty acids and long chain alcholos

Steroids: insoluble in water

*basic structure

Cholesterol - precursor for sex hormones

Carotenoids - carotene - yellow pigment of veggies (Vit. A precursor)

Monogastrics

Digestion: goal = TG ® MG + 2 FA ® absorbed

TG insoluble ® must become soluble

1. Course emulsion is formed - (Fat globule) in stomach - HCl

2. Bile acts to form droplet - duodenum

3. Lipase acts at the fat:water interface and cleaves FA #1 and #3

4. Micelles - 2MG, FFA & bile salts are formed with polar (hydrophilic) on outside and non-polar (lipophilic) on inside of micelle

5. upon contact with microvilli in duodenum - MG & FFA absorbed

6. as absorbed, MD & FA are immediately resynthesized to TG and Phospholipids

7. TG droplets enveloped by lipoprotein - chylomicron - exits cell to lymph system (NOT BLOOD!!)

8. Glycerol is passively absorbed

9. short chain FA (more water soluble) are absorbed without chylomicron, and go to the blood. If #2 FA is short chain, goes to lymph!

 

Post-Absorption:

1. Stored as fat in adipose tissue - (constant turnover)

2. Converted to acetyl - CoA via b -oxidation

acetyl CoA can be used for energy (NOT glucose), synthesis of fat, or formation of ketone body.