Metabolic pathways Original Scenario-Based Download PDF

Questions

1. 1.

   In an engineered bio-luminescent lichen, glowing pigment $P$ is synthesized from precursor $S$ across a multi-step pathway governed sequentially by enzymes $E_1$, $E_2$, and $E_3$. As pigment $P$ accumulates beyond optimal cellular levels, it reversibly binds to an allosteric site on the first pathway-specific enzyme, $E_1$, temporarily halting its activity. If a mutation permanently locks $E_1$ into an active conformation insensitive to pigment $P$, what is the most direct consequence on this metabolic pathway?

   • A) The pathway will immediately reverse its direction, converting excess pigment $P$ back into precursor $S$ via enzymes $E_3$, $E_2$, and $E_1$.
   • B) Synthesis of intermediate metabolites will cease completely, triggering pathway degradation due to lack of substrate affinity.
   • C) Intermediate metabolites and pigment $P$ will continuously accumulate at the expense of precursor $S$ and cellular energy resources.
   • D) The organism will selectively switch enzymes $E_2$ and $E_3$ to catabolic breakdown of precursor $S$, bypassing pigment formation.