Metabolic pathways Transitional Reasoning Download PDF

Questions

1. 1.

   In a bacterial metabolic pathway, initial precursor S is converted into end-product P through sequential intermediates X and Y by three specific enzymes: $S \xrightarrow{E_1} X \xrightarrow{E_2} Y \xrightarrow{E_3} P$. Under normal conditions, accumulation of the end-product P allosterically inhibits the first committed enzyme, $E_1$, to regulate flux through the pathway. If a loss-of-function mutation completely inactivates enzyme $E_2$ while precursor S is continuously supplied, how will the concentrations of metabolite X and product P, as well as the regulatory status of enzyme $E_1$, be affected?

   • A) Intermediate X will decrease, end-product P will remain stable, and enzyme $E_1$ will become irreversibly inactivated by precursor S.
   • B) Intermediate X will be diverted directly into end-product P, leading to an overproduction of P and constant allosteric inhibition of enzyme $E_1$.
   • C) Intermediate X will remain unchanged because enzyme $E_3$ compensates for the missing step, maintaining standard levels of product P and normal feedback inhibition.
   • D) Intermediate X will accumulate, end-product P will become depleted, and enzyme $E_1$ will remain active due to the relief of feedback inhibition.