Monomeric subunits of proteins can sometimes assemble into higher order assemblies. Two such related human proteins $\mathbf{P}$ and $\mathbf{Q}$ assemble into hexamers by sequential assembly of their subunits. However, while $\mathbf{P}$ assembles into a hexameric ring, $\mathbf{Q}$ assembles into a linear hexameric arrangement as shown in the figure. Only hexameric assemblies of the proteins are functional.




The equilibrium constants for association $\left(K_1, K_2, K_3\right.$, and $\left.K_4\right)$ of subunits at each step until pentamers are assembled, both for $\mathbf{P}$ and $\mathbf{Q}$, are the same $\left(10^5\right)$. However, the equilibrium association constant of the final step of assembly into a hexamer is drastically different, $10^{10}$ for P and $10^5$ for Q . Based on this information, choose the statement(s) that is(are) likely to be true.

• A

  For $\mathrm{Q}, \Delta \mathrm{G}^{\circ}$ at the final step of assembly is half as much as the earlier step.
• Correct answer
  B

  Cellular concentration of Q must be higher than that of P .
• C

  For all steps in assembling P and $\mathrm{Q}, \Delta \mathrm{G}^{\circ}$ remains the same.
• Correct answer
  D

  For $\mathrm{P}, \Delta \mathrm{G}^{\circ}$ at the final step of assembly is twice that of the earlier step.

Hence, the correct answer is options: 'B', 'D'.