Question

Fatty Acid Metabolism. The reactions of the fatty acid spiral are shown below. Use the description on the left side of the page to classify the reactions and fill in the boxes on the right side of the page Activation Step. The activation of the fatty acid begins by the addition of CoA which will carry the fatty acid from the cytosol into the mitochondria. The product, which is a fatty acid with a CoA attached, is known as a fatty acyl-CoA "Acyl" is a general term used when the group attached to CoA is anything other than two carbons. This activation step is endergonic and requires 1 ATP molecule which is converted to 1 AMP molecule (2 phosphates are cleaved). This activation step is only performed once for each fatty acid, while steps 1-4 are repeatedly cycled to cleave two carbons from the fatty acid each cycle Activation Step Step . This is the beginning of the "spiral". You should be able to identify this metabolic reaction by comparing it to the reactions shown on the previous page. Try to classify it by noticing the changes from reactants to products. If you need a hint, recall your definitions of oxidation and reduction reactions Step 1 Classity Reaction Oxidation: increase C-O bonds OR decrease C-H bonds . Reduction: decrease C-O bonds OR increase C-H bonds Since this is an oxidation reduction reaction, a cofactor is required and the type of oxidation will help you identify the proper cofactor Step 2. This common metabolic reaction was NOT shown on the previous page. Don't make the mistake of classifying this as an oxidation or a reduction. It may look like an oxidation because there is a new C-O bond, but there an "H" and an "OH is added In this type of reaction, a cofactor is typically not necessary, but you must add a compound to provide the "H" and the "OH Sep 2 Classify Readtion Step 3. This is another metabolic reaction that you should be able to identify by comparing it to the reactions on the previous page Again, by comparing the reactant and the product and you should note that an alcohol converts to a ketone. Note that this reaction produces the second cofactor that can be used to produce ATP Step 3 Classify Reacton Step 4. The last reaction is not a typical metabolic reaction and is a classified as a cleavage reaction. This step requires an extra Co- A as a cofactor and the reaction breaks our substrate into two separate products. The product on the right, acetyl-CoA, continues to stage 3 of metabolism (the citric acid cycle). The product on the left, fatty acyl-CoA is two carbons shorter than the starting molecule. This metabolic process is known as a "spiral" because this molecule proceeds to step 1 again to cleave off two more carbons. More specifically in this example, the fatty acyl-CoA at the bottom of the page will go through the fatty acid spiral 2 more times producing 3 acetyl-CoA molecules 2. Lipogenesis. The reactions of the lipogenesis are shown below. Use the description on the left side of the Step 4 Classity Reaction: S-COA faty acyl-CoA acetyl-CoA page to classify the reactions and fill in the boxes on the right side of the page -78-

Answer 1

Beta-oxidation of Behenic acid:
It is a 22C containing saturated fatty acid.
1 NADH = 2.5 ATP
1 FADH2 = 1.5 ATP

1. Number of carbon atoms = 22
2. Number of acetyl CoA produced = 22/2 = 11
3. Number of beta-oxidation cycles = (22/2)-1 = 10
4. Number of NADH produced from the fatty acid spiral = 10
5. Number of FADH2 produced from the fatty acid spiral = 10
6. Number of ATP produced from Acetyl CoA by TCA cycle = 11 X 10 = 110
7. Number of ATP produced from NADH = 10 X 2.5 = 25
8. Number of ATP produced from FADH2 = 10 X 1.5 = 15
9. Total ATP produced = 110+25+15 = 150
10. Number of ATP required for activation = 2
11. Net yield = 148 ATP

Beta-Oxidation cycle 0 H2O FAD FADH 2/ 0 Oxidation Hydration НН Acyl CoA trans-A*-Enoyl CoA L-3-Hydroxyacyl CoA NAD+ 3 |Oxidation H +NADH OA 0 0 Thiolysis НН Acyl CoA (-2C) Acetyl CoA 3-Ketoacyl CoA 1- Acyl CoA dehydrogenase 3 3-Hydroxyl acyl CoA dehydrogenase 2- Enoyl CoA hydratase 4- Beta-keto acyl CoA thiolase