For the first step in fatty acid catabolism, we say that ATP is used to “drive” the reaction that links the fatty acid with coenzyme-A. Without ATP hydrolysis, would you predict that the linking of fatty acid to coenzyme-A would be ­exergonic or endergonic? In fatty acid CoA synthesis, the hydrolysis of the ATP portion is based on what major strategy of metabolism?

Verified step by step guidance

1. Understand the terms 'exergonic' and 'endergonic': An exergonic reaction releases energy, while an endergonic reaction requires an input of energy.
2. Consider the role of ATP in the reaction: ATP hydrolysis provides energy, suggesting that the reaction without ATP would likely be endergonic, as it requires energy input.
3. Recognize that ATP hydrolysis is a common strategy in metabolism to make unfavorable reactions proceed by coupling them with favorable ones.
4. Identify the major strategy of metabolism involved: The hydrolysis of ATP is an example of energy coupling, where an energetically unfavorable reaction is driven by a favorable one.
5. Conclude that without ATP, the linking of fatty acid to coenzyme-A would be endergonic, as it relies on the energy provided by ATP hydrolysis to proceed.

Key Concepts

ATP Hydrolysis

ATP hydrolysis is the process by which adenosine triphosphate (ATP) is broken down into adenosine diphosphate (ADP) and inorganic phosphate (Pi), releasing energy. This energy is often used to drive endergonic reactions, which require an input of energy to proceed. In the context of fatty acid catabolism, ATP hydrolysis provides the necessary energy to link fatty acids to coenzyme-A, facilitating their activation for further metabolic processes.

Exergonic vs. Endergonic Reactions

Exergonic reactions are those that release energy, typically occurring spontaneously, while endergonic reactions require an input of energy to proceed. The linking of fatty acids to coenzyme-A is an endergonic process, as it involves the formation of a high-energy thioester bond. The energy from ATP hydrolysis is crucial in making this reaction favorable, effectively coupling the two types of reactions to ensure metabolic efficiency.

Metabolic Coupling

Metabolic coupling refers to the strategy of linking exergonic and endergonic reactions to drive biological processes. In fatty acid CoA synthesis, the hydrolysis of ATP is coupled with the activation of fatty acids, allowing the energy released from ATP breakdown to facilitate the otherwise unfavorable reaction of fatty acid attachment to coenzyme-A. This coupling is a fundamental principle in metabolism, ensuring that energy is efficiently utilized in cellular processes.