What is the number of ATP molecules produced by the beta oxidation of eicosanoic acid?
To determine the number of ATP molecules produced by the beta oxidation of eicosanoic acid, we need to understand the process of beta oxidation and the ATP yield from each step.
First, let's break down the process of beta oxidation. Beta oxidation is the metabolic pathway responsible for the breakdown of fatty acids into acetyl-CoA units, which can then enter the citric acid cycle (also known as the Krebs cycle) to produce ATP.
For every round of beta oxidation, the following steps occur:
1. Activation: Two ATP molecules are consumed to activate the fatty acid, requiring two ATP molecules.
2. Cleavage: Each round of beta oxidation removes two carbon units, known as an acetyl-CoA molecule, from the fatty acid chain. This generates one molecule of FADH2 and one molecule of NADH, which are electron carriers that can produce ATP in subsequent cellular processes.
3. Oxidation: For each acetyl-CoA molecule generated in the cleavage step, three NADH molecules and one FADH2 molecule are produced. These electron carriers will be used in the electron transport chain to generate ATP.
4. Thioester cleavage: The final step of beta oxidation involves releasing the last acetyl-CoA molecule, producing another molecule of NADH.
Now, let's apply this information to the specific case of eicosanoic acid, which is a 20-carbon fatty acid.
Since each round of beta oxidation removes two carbon units, eicosanoic acid will undergo nine rounds of beta oxidation to produce ten acetyl-CoA molecules. Therefore, we can calculate the number of ATP molecules produced as follows:
Activation step: 2 ATP consumed × 9 rounds = 18 ATP consumed
Cleavage step: 1 FADH2 molecule per round × 9 rounds = 9 FADH2
Oxidation step: 3 NADH molecules per round × 9 rounds = 27 NADH
Thioester cleavage step: 1 NADH molecule = 1 NADH
Now, let's calculate the overall ATP yield from the FADH2 and NADH molecules:
Each FADH2 molecule can generate approximately 1.5 ATP molecules in the electron transport chain.
Each NADH molecule can generate approximately 2.5 ATP molecules in the electron transport chain.
Therefore, the ATP yield from the FADH2 and NADH molecules is as follows:
FADH2: 9 FADH2 × 1.5 ATP = 13.5 ATP
NADH: 27 NADH × 2.5 ATP = 67.5 ATP
Thioester cleavage: 1 NADH = 1 ATP
Adding up the ATP produced from each step:
Activation: -18 ATP
Cleavage: 0 ATP (no ATP produced or consumed)
Oxidation: 13.5 ATP (from FADH2) + 67.5 ATP (from NADH) = 81 ATP
Thioester cleavage: 1 ATP
Finally, let's sum up the ATP produced:
18 ATP (consumed) + 0 ATP (cleavage) + 81 ATP (oxidation) + 1 ATP (thioester cleavage) = 100 ATP molecules produced from beta oxidation of eicosanoic acid.
Therefore, the beta oxidation of eicosanoic acid generates approximately 100 ATP molecules.