[Campbell Biology P.212] Consider the branched metabolic reaction pathway described: L can f... | Practice Question

Consider the branched metabolic reaction pathway described: L can form either M or N. M can form O. O can form either P or R. P can form Q. R can form S. O inhibits the reaction of L to form M. Q inhibits the reaction of O to form P. S inhibits the reaction of O to form R. Which reaction would prevail if both Q and S were present in the cell in high concentrations?

  • A: L→M
  • B: M→O
  • C: L→N
  • D: O→P

Explanation

When Q and S are in high concentrations, they inhibit their respective upstream reactions O→P and O→R . This leads to an accumulation of O. Since O inhibits the L→M reaction, the pathway from L will be shunted towards N, making L→N the prevailing reaction.