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.

b -Oxidation - O2 needed, so in the mitochondria.

Break down of fat to acetyl-CoA

One fatty acid goes through several cycles.

1 Cycle

1. takes off 2C - acetyl-CoA - 12 ATP

2. 1 FADH2

3. 1 NADH

Takes 2 ATP to activate (initial investment)

Examples:

Caproic Acid C6:0 ® C6H12O2

2 cycles of b -oxidation ®

3 acetyl CoA X 12 = 36 ATP

2 turns of cycle X 5 = 10 ATP

= 46 ATP - 2 ATP (initial investment) yields 44 ATP

Glucose only yields 36 ATP.