What is the net gain of ATP from one round of fatty acid synthesis?

In fatty acid synthesis, the process generally requires energy input in the form of ATP to convert acetyl-CoA into fatty acids. Specifically, during the conversion of acetyl-CoA to malonyl-CoA, an ATP molecule is consumed, and this is balanced by the energy produced later during the breakdown of fatty acids through β-oxidation.

It's important to note that while ATP is consumed in building fatty acids, the process does not directly produce ATP. Instead, it uses energy, and there is effectively no net gain in ATP from the synthesis process itself. Because of this, the total balance during one round of fatty acid synthesis leads to a net gain of zero ATP.

Therefore, the correct answer reflects that the fatty acid synthesis process does not yield ATP, aligning with the understanding that the energy investment primarily accounts for the synthesis rather than net production.