What is the concerted model in the context of allosteric enzymes?

• A. A model that describes the conversion of subunits only in the presence of substrate.
• B. A model that describes the conversion of subunits in a sequential manner.
• C. A model that describes the independent conversion of subunits between the T state and R state.
• D. A model that describes the simultaneous conversion of all subunits between the T state and R state.

Answer: (D)