Answer:
ATP acts as a regulatory molecule in multiple steps of the citric acid cycle:
Explanation:
In the citric acid cycle, the 2 pyruvate molecules formed can either be converted to Acetyl Co-A or stored as lipids. As the enzyme, pyruvate dehydrogenase has to make this decision, this step of the TCA cycle is a crucial control point of the pathway. Pyruvate dehydrogenase is activated when phophorylated by a kinase but deactivated in the presence of high amount of ATP by a phosphatase enzyme. On the contrary, the presence of high ADP activates the complex.
ADP or a low energy signal allosterically activates the isocitrate dehydrogenase that converts isocitrate to a five carbon alpha-ketoglutarate. High ATP inhibits the enzyme.
The enzyme, α-ketoglutarate dehydrogenase converts alpha ketoglutarate to a four carbon compound, succinyl Co-A. Here, ATP also acts as an inhibitor.