The pyruvate dehydrogenase complex is subject to allosteric control, especially inhibition by reaction products. The main regulatory process controlling pyruvate dehydrogenase's activity in eukaryotes is a. exchange of ADP and ATP on the pyruvate dehydrogenase complex.
b. phosphorylation by ATP, which turns the complex on, and dephosphorylation, which turns the complex off.
c. AMP binding to and activating the enzyme.
d. phosphorylation by ATP, which turns the complex off, and dephosphorylation, which turns the

D. Phosphorylation by ATP, which turns the complex off, and dephosphorylation, which turns the complex on.

Explanation:

The pyruvate dehydrogenase complex (PDH) is responsible for the conversion of pyruvate to acetylCoA, the fuel for the citric acid cycle.

The regulation of the activity of PDH is allosterically by the products of the reaction which it catalyses. These products are ATP, acetylCoA and NADH. When their is sufficient fuel available for the needs of the cells in the form of ATP, the complex is turned off by phosphorylation of one of the two subunits of E1 (pyruvate dehydrogenase). This phosphorylation inactivates E1. When the concentration of ATP declines, a specific phosphatase removes the phosphoryl group from E1, thereby activating the complex again.

dynamic equilibrium is the answer.

a) the particles of the chair are strongly held together.