Energy coupling Original Scenario-Based Download PDF

Questions

1. 1.

   In the crystalline mantle of the subterranean silicate-weaver slug, cells construct rigid structural silin-fibers through an endergonic condensation pathway with a standard free-energy change of $\Delta G = +19.2\text{ kJ/mol}$. Metabolic analysis reveals that the weaver cells drive this unfavorable synthesis by coupling it directly to the exergonic hydrolysis of ATP, which exhibits a $\Delta G = -30.5\text{ kJ/mol}$. Which mechanism best explains how the weaver cell successfully couples these two reactions to make silin-fiber polymerization thermodynamically favorable?

   • A) The cell releases the free energy from ATP hydrolysis entirely as thermal vibrations that warm the surrounding cytoplasm to overcome the activation barrier.
   • B) The cell uses ATP to bind non-covalently to the silin monomers, acting purely as an allosteric inhibitor to halt competing catabolic pathways.
   • C) The cell transfers a phosphate group from ATP to a monomer precursor to form a reactive, high-energy phosphorylated intermediate that makes the net free-energy change negative.
   • D) The cell utilizes ATP hydrolysis to alter the equilibrium constant of the silin-fiber condensation without directly participating in the chemical reaction steps.