Where does the first carbon come from in fatty acid synthesis?

[samy4408]

Hello , in the course of fatty acids synthesis the professor said that after the repetition of the cycle 7 times we end up with a 16 carbon chain
and he added that all the carbons came from acetyl-COA except for one .
i didn't understand the last one , what is the carbon that don't come from acetyl-COA ?

 

[Godot_]

In even-chained fatty acids, this also is from AcCoA.
In odd-chained (e.g. C15 or C17), however, the initial element is Propionyl-CoA.

HTH

 

[samy4408]

thanks a lot !