BETA OXIDATION OF FATTY ACIDS,Fatty acid oxidation —stages and tissues.pptx

PPT on Beta-oxidation of Fatty acid. The fatty acids in the body are mostly
oxidized by 􀁅-oxidation. 􀁅-Oxidation may be
defined as the oxidation of fatty acids on the
􀁅-carbon atom. This results in the sequential
removal of a two carbon fragment, acetyl CoA.The ultimate aim of fatty acid oxidation is to
generate energy.Activation of fatty acids occurring in the
cytosol.Transport of fatty acids into mitochondria.􀁅-Oxidation proper in the mitochondrial
matrix.

1. BETA OXIDATION OF FATTY ACIDS

2. Substrate: Fatty acid Product: Acetyl CoA (2-carbon compound) Compartment: Mitochondria Site: Liver, Heart, skeletal muscle, adipose tissue Coenzyme: NAD, FAD

3. This process is known as beta-oxidation because the oxidation and splitting of two carbon units occur at the beta-carbon atom. The major pathway for catabolism of fatty acids is a mitochondrial pathway called β-oxidation, in which two-carbon fragments are successively removed from the carboxyl end of the fatty acyl CoA, producing acetyl CoA, NADH, and FADH2.

4. OXIDATION OF FATTY ACIDS OCCURS IN MITOCHONDRIA

5. Fatty Acids Are Transported in the Blood as Free Fatty Acids Free fatty acids (FFAs)—also called unesterified (UFA) or nonesterified (NEFA) fatty acids —are fatty acids that are in the unesterified state. In plasma, longer chain FFA are combined with albumin, and in the cell they are attached to a fatty acid binding protein, so that in fact they are never really “free.” Shorter chain fatty acids are more water-soluble and exist as the unionized acid or as a fatty acid anion.

6. Role of carnitine in the transport of long chain fatty acids through the inner mitochondrial membrane. Carnitine ( β - hydroxy- γ- trimethylammonium butyrate), is widely distributed and is particularly abundant in muscle.

7. Long-chain acyl-CoA enters the intermembrane space after its formation by acyl-CoA synthetase , but cannot pass through the inner mitochondrial membrane. For transport across the membrane, therefore, acyl groups are transferred from CoA to carnitine by carnitine palmitoyl transferase I (embedded in the outer mitochondrial membrane). The acylcarnitine formed can then be carried into the mitochondrial matrix by carnitine acylcarnitine translocase (embedded in the inner mitochondrial membrane) in exchange for a free carnitine. The acyl group is then transferred back to CoA by carnitine palmitoyl transferase II, reforming acyl-CoA, and the carnitine released is transported back into the intermembrane space via the translocase enzyme.

8. β - OXIDATION OF FATTY ACIDS INVOLVES SUCCESSIVE CLEAVAGE WITH RELEASE OF ACETYL COA In the β -oxidation pathway, two carbons at a time are cleaved from acyl-CoA molecules, starting at the carboxyl end. The chain is broken between the α (2)- and β (3)- carbon atoms—hence the name β -oxidation. The two-carbon units formed are acetyl-CoA; thus, palmitoyl-CoA forms eight acetyl-CoA molecules.

9. The ultimate aim of fatty acid oxidation is to generate energy. The energy obtained from the complete oxidation of palmitic acid (16 carbon) Number of β -oxidation cycle (X-2) /2 =7 Number of acetyl CoA 16/2=8 X= number of carbon atom

10. Oxidation of a Fatty Acid With an Odd Number of Carbon Atoms Yields Acetyl-CoA Plus a Molecule of Propionyl-CoA Fatty acids with an odd number of carbon atoms are oxidized by the pathway of β -oxidation described above producing acetyl CoA until a three-carbon (propionyl-CoA) residue remains. This compound is converted to succinyl-CoA, a constituent of the citric acid cycle. Hence, the propionyl residue from an odd-chain fatty acid is the only part of a fatty acid that is glucogenic. Number of β -oxidation cycle (X-3) /2 X= number of carbon atom

11. How many ATP will produce from 17C fatty acid oxidation Odd number fatty acid oxidation ATP calculation 17C---- 7 β -oxidation cycle = 7 acetyl CoA molecule = 7 12= 84 ATP(TCA Cycle) NADH + H + = 7 3= 21 ATP FADH 2 = 7 2=14 ATP NET ATP= 84+21+14 =119 = 119 Energy utilized 2 ATP 119-2= 117ATP.  

12. Now from propionyl CoA to succinyl CoA 1 ATP loss for activation succinyl CoA enters the TCA cycle NADH+H + = 1 3 = 3ATP FADH 2 = 1 2 = 2 ATP GTP = 1 ATP Total= 6 ATP 1 ATP loss for activation= 5 ATP Net total 122+5= 122  ATP