Ladies and gentlemen, your Biochemistry Adventure is nearly at an end. Over the

Question

Ladies and gentlemen, your Biochemistry Adventure is nearly at an end. Over the course of three exams you have Your mission, should you chose to accept it is to determine the total number of ATP produced in the complete catabolism of the triacyl glycerol shown below. Fatty Acid chains are highlighted. FA3 FA1 FA2 Now I have a few hints and details. I would suggest using a divide and conquer approach, as each subcomponent of the total catabolism that you correctly determine the number of ATP will in fact earn you points in addition to simply finding the total number of ATP for the entire process. In essence, you can receive partial credit by showing your stepwise summations for each FA. You make work out the processes first on paper, but I would appreciate you completing your summation analysis in Excel by making tables, which may, in fact, help stop you from committing math errors. You will have multiple processes to consider as suggested below: 1) 2) 3) 4) 5) Transport into and out of the mitochondria ?-Oxidation Glycolysis The Citric Acid Cycle Electron Transport Additionally, there is an enzyme that we did not particularly discuss in class, but you could find useful here. It is Malic Enzyme, which can be used to convert malate via decarboxylation into pyruvate in the cytosol. This might have a creative use Malate NADP-PyruvateCO2 + NADPH Lastly, consider ATP equivalents. GTP is equivalent to ATP. Cleavage of ATP into AMP is worth a -2 ATP equivalents. Also, consider any NADH from glycolysis to utilize the Malate-Aspartate Shuttle rather than taking an FADH2 route. Lastly, make every attempt to take the path that yields the most ATP when in doubt. If you do have questions on what I expect, or a very good thought question, I will provide you with as much clarification as possible without a simple reveal of the final answer

Explanation / Answer

Beta oxidation glycerolaldehyde:

According to the Beta oxidation both saturated fatty acids and unsaturated fatty acids can produce equal amount of energy. The main product produced in the Beta oxidation is Acetyl CoA. But in odd chain fatty acids PropinylCoA (last 3 carbons) is produced at last step.

Every fatty acid molecule undergoes beta oxidation to give rise to acetyl-CoA and the rest of the molecule in each of the oxidation step. For example, a 16C fatty acid will divide into a 14C molecule and acetyl CoA in one step and releases 5 molecules of ATP in this step. At the end of the process, the number of steps multiplied by 5 will give the number of ATP molecules released.

After the release of acetyl-CoA molecules, each of these will again combine with two oxygen molecules to give rise to 12 ATP molecules. The total number of ATPs released can be calculated based on the number of acetyl CoAs released.

Therefore, the entire ATP from the previous process is added to that of the acetyl CoA oxidation process to get the total number of ATP molecules released in the entire beta oxidation of the fatty acid. But, every fatty acid molecule takes in 2 ATP molecules to undergo beta oxidation. So, 2ATP are removed from the total released ATP molecules to get the net gain of ATP molecules in the entire beta oxidation.

Now, coming to the current problem excluding the backbone glycerol, there are 18C, 8C and 9C fatty acid chains that have to undergo beta oxidation.

Beta oxidation of fatty acids:

Number of ATP's produced per rounds of Beta oxidation = 5 (1 NADH + 1 FADH2)

Number of ATP's produced per rounds from Acetyl CoA via TCA cycle = 12

FA 1: 18 carbon chain

Stearic acid:

Number of rounds of Beta oxidation = 8

Number of Acetyl CoA produced = 9

   ATP produced in Beta oxidation- 8 X 5 = 45

   ATP produced by Acetyl CoA in TCA cycle - 9 X 12 = 108

       45 + 108 = 148

For activation of Stearic acid requires 2 ATP's is required,

So 148 ATP - 2 ATP = 146 ATP is produced from 1 Stearic acid.

FA 2: 8 Carbon chain

Caprylic acid:

Number of rounds of Beta oxidation = 4

Number of Acetyl CoA produced = 5

   ATP produced in Beta oxidation- 4 X 5 = 20

   ATP produced by Acetyl CoA in TCA cycle - 5 X 12 = 60

       20 + 60 = 80

For activation of Caprylic acid requires 2 ATP's is required,

So 80 ATP - 2 ATP = 78 ATP is produced from 1 Caprylic acid.

FA 3: 9 carbon chain

Pelargonic acid:

Number of rounds of Beta oxidation = 4

Number of Acetyl CoA produced = 5

   ATP produced in Beta oxidation- 4 X 5 = 20

   ATP produced by Acetyl CoA in TCA cycle - 5 X 12 = 60

       20 + 60 = 80

For activation of Pelargonic acid requires 2 ATP's is required,

So 80 ATP - 2 ATP = 78 ATP is produced from 1 Pelargonic acid.

The remaining last 3 carbons are released as propinylCoA

ATP's produced from Glyceride:

Glycerol is a 3 carbon molecule, so complete oxidation of glycerol can produce 3 Co2.

Total ATP from glycerol:

STEP 1 : Glycerol ---> Glycerol 3-phosphate -1 ATP

STEP 2 :.Glycerol 3-phosphate ---> Dihydroxy actone phosphate 2.5 ATP (1 NADH)

STEP 3 : Glycerol 3-phosphate ---> Pyruvate 4,5 ATP(1 NADH,2 ATP)

STEP 4 : Pyruvate ---> Acetyl-coA 2.5 ATP(1 NADH)

STEP 5 : Krebs cycle 10 ATP (3 NADH + 1 FADH + 1GTP)

NET TOTAL= 19.5 ATP - 1 ATP ( for step 1 activation) = 18.5 ATP

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