1. Chapter 25 Metabolic Pathways for Lipids and Amino Acids
25.1 Digestion of Triacylglycerols
25.2 Oxidation of Fatty Acids
25.3 ATP and Fatty Acid Oxidation

2. Digestion of Triacylglycerols
In the digestion of fats (triacylglycerols):
Bile salts break fat globules into micelles in the small intestine.
Pancreatic lipases hydrolyze ester bonds to form monoacylglycerols and fatty acids, which recombine in the intestinal lining.
Lipoproteins form and transport triacylglycerols to the cells of the heart, muscle, and adipose tissues.

3. Digestion of Triacylglycerols

4. Fat Mobilization Fat mobilization:
Breaks down triacylglycerols in adipose tissue to fatty acids and glycerol.
Fatty acids are hydrolyzed initially from C1 or C3 of the fat.
Triacylglycerols + 3H2O Glycerol + 3Fatty acids

5. Fatty Acid Activation Fatty acid activation:
Allows the fatty acids in the cytosol to enter the mitochondria for oxidation.
Combines a fatty acid with CoA to yield fatty acyl CoA that combines with carnitine.

6. Fatty Acid Activation
Fatty acyl-carnitine transports the fatty acid into the matrix.
The fatty acid acyl group recombines with CoA for oxidation.

7. Fatty Acid Activation
Fatty acid activation is complex, but it regulates the degradation and synthesis of fatty acids.

8. Beta-Oxidation of Fatty Acids
In reaction 1, oxidation:
Removes H atoms from the  and  carbons.
Forms a trans C=C bond.
Reduces FAD to FADH2.
 

9. Beta-Oxidation of Fatty Acids
In reaction 2, hydration:
Adds water across the trans C=C bond.
Forms a hydroxyl group (—OH) on the  carbon.
 

10. Beta ()-Oxidation of Fatty Acids
In reaction 3, a second oxidation:
Oxidizes the hydroxyl group.
Forms a keto group on the  carbon.
 

11. Beta ()-Oxidation of Fatty Acids
In Reaction 4, acetyl CoA is cleaved:
By splitting the bond between the  and  carbons.
To form a shortened fatty acyl CoA that repeats steps of -oxidation.

12. Beta ()-Oxidation of Myristic (C14) Acid

13. Beta ()-Oxidation of Myristic (C14) Acid (continued)
7 Acetyl CoA
6 cycles

14. Cycles of -Oxidation The length of a fatty acid:
Determines the number of oxidations and
The total number of acetyl CoA groups.
Carbons in Acetyl CoA -Oxidation Cycles
Fatty Acid (C/2) (C/2 –1)

15. -Oxidation and ATP Activation of a fatty acid requires: 2 ATP
One cycle of oxidation of a fatty acid produces:
1 NADH ATP
1 FADH ATP
Acetyl CoA entering the citric acid cycle produces:
1 Acetyl CoA 12 ATP

16. ATP for Lauric Acid C12 ATP production for lauric acid (12 carbons):
Activation of lauric acid ATP
6 Acetyl CoA
6 acetyl CoA x 12 ATP/acetyl CoA 72 ATP
5 Oxidation cycles
5 NADH x 3ATP/NADH 15 ATP
5 FADH2 x 2ATP/FADH ATP
Total ATP