Your text describes three stages in fatty acid catabolism. The second of these i
ID: 861404 • Letter: Y
Question
Your text describes three stages in fatty acid catabolism. The second of these is "activation" -- the synthesis of acylCoA (or fatty-acylCoA) molecules from HSCoA and free fatty acids. What is TRUE about fatty acid activation?
A. PPi released from ATP in synthesis of an acyl-CoA is hydrolyzed to 2 Pi, to make the acylCoA synthesis irreversible.
B. AcylCoA synthesis does not require the expenditure of energy (in the form of ATP hydrolysis, for instance)
C. A fatty acid is joined to HSCoA in a phosphoanhydride linkage.
D. This step (activation) is optional in fatty acid catabolism; it's not strictly necesarry for breakdown of a fatty acid.
Explanation / Answer
Long fatty acids are activated by acyl CoA.
In this activation, first fatty acid reacts with ATP to given an acyl-adenylate and pyrophosphate then CoA attacks the acyl adenylate to give acyl-CoA and AMP.
Fatty acid + ATP +CoA = acyl-CoA + AMP + PPi
This reaction is reversible.
The reaction becomes irreversible if we couple the activity of the enzyme inorganic pyrophosphatase.
Fatty acid + ATP +CoA = acyl-CoA + AMP + 2Pi
Therefore, the true statement is A. PPi released from ATP in synthesis of an acyl-CoA is hydrolyzed to 2 Pi, to make the acylCoA synthesis irreversible.
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