ATP in Fatty acid oxidation and citric acid cycle

In summary, the question is asking at what point in beta-oxidation or the citric acid cycle is ATP used. The answer is that during the citric acid cycle, ATP is produced during the conversion of succinyl CoA to Succinate, but it is not required anywhere in the cycle. However, during beta-oxidation, 2 ATP are used during fatty acid activation, with one being used when the fatty acid is added to ATP to form acyladenylate. The other ATP may be required during the hydrolysis of the resulting pyrophosphate, but it is unclear when this occurs. Additionally, when dealing with odd number fatty acid degradation, the final product, propionyl CoA, is
  • #1
jenzao
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At what point in either beta-oxidation or citric acid cycle is ATP used?
I see where ATP is produced in citric acid cycle (originally as GTP) as when succinyl CoA is converted to Succinate, but I can't find any part where ATP is required. Apparently according to my lecture notes, it is required during beta oxidation somewhere but I can't see exactly where? Please help, thanks!

UPDATE: i found out that the 2 ATP are used during fatty acid activtion, but I only see where one is required. (??)

(when fatty acid is added to 1 ATP to form acyladenylate) Where is other one required?? thanks
 
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  • #2
jenzao said:
At what point in either beta-oxidation or citric acid cycle is ATP used?
I see where ATP is produced in citric acid cycle (originally as GTP) as when succinyl CoA is converted to Succinate, but I can't find any part where ATP is required. Apparently according to my lecture notes, it is required during beta oxidation somewhere but I can't see exactly where? Please help, thanks!

UPDATE: i found out that the 2 ATP are used during fatty acid activtion, but I only see where one is required. (??)

(when fatty acid is added to 1 ATP to form acyladenylate) Where is other one required?? thanks
Could the question be referring to the hydrolysis of the resulting pyrophosphate?

Fatty acid + ATP <-----> Acyl adenylate + PPi
PPi + pyrophosphatase -------> 2Pi

What about odd number fatty acid degradation? How is the final product (propionyl CoA) dealt with?
 
  • #3


I am happy to clarify this confusion for you. In both fatty acid oxidation and the citric acid cycle, ATP is used at specific points in the process to provide energy for the reactions to occur.

In fatty acid oxidation, ATP is used during the activation step when the fatty acid is attached to Coenzyme A (CoA) to form fatty acyl-CoA. This reaction requires the hydrolysis of one ATP molecule to ADP and inorganic phosphate (Pi). This is necessary to activate the fatty acid and prepare it for further breakdown.

In the citric acid cycle, ATP is used during the conversion of succinyl-CoA to succinate. This reaction is catalyzed by the enzyme succinyl-CoA synthetase, which uses the energy from the hydrolysis of GTP to produce ATP. This is why GTP is often referred to as the "energy equivalent" of ATP.

To answer your question about the second ATP in fatty acid activation, it is not directly used in the reaction but rather produced as a byproduct. During the reaction, Coenzyme A is released and recycled, and in the process, it produces ATP from ADP and Pi. This is why there is a net gain of 2 ATP molecules in the activation of one fatty acid molecule.

I hope this clarifies the role of ATP in fatty acid oxidation and the citric acid cycle. It is important to note that ATP is constantly being produced and used in these processes to provide energy for the cell to carry out its functions.
 

1. What is the role of ATP in fatty acid oxidation?

ATP is used as an energy source during fatty acid oxidation. As fatty acids are broken down, they release energy which is used to convert ADP into ATP. This ATP can then be used by cells for various biological processes.

2. How does ATP play a role in the citric acid cycle?

In the citric acid cycle, ATP is produced through a series of reactions that occur in the mitochondria. This process, known as oxidative phosphorylation, uses the energy released from the breakdown of glucose and other molecules to convert ADP into ATP.

3. How is ATP generated during fatty acid oxidation and the citric acid cycle?

During fatty acid oxidation, ATP is generated through the process of beta-oxidation. This process breaks down fatty acids into smaller molecules, releasing energy that is used to generate ATP. In the citric acid cycle, ATP is generated through oxidative phosphorylation, as mentioned in the previous answer.

4. What happens to ATP in the citric acid cycle?

In the citric acid cycle, ATP is used as an energy source to drive various reactions. It is also produced through oxidative phosphorylation, as discussed earlier. Overall, ATP plays a crucial role in providing energy for the citric acid cycle to occur.

5. Is ATP the only energy source used in fatty acid oxidation and the citric acid cycle?

No, ATP is not the only energy source used in these processes. Other molecules, such as NADH and FADH2, also play important roles in providing energy for fatty acid oxidation and the citric acid cycle. These molecules are produced during the breakdown of fatty acids and are used to generate even more ATP through oxidative phosphorylation.

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