Using a series of arrows, draw the branched metabolic reaction pathway described by the following statements, and then answer the question at the end. Use red arrows and minus signs to indicate inhibition. 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 Oto 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

1) The branched metabolic reaction pathway is attached.

2) The most prevalent reaction is L-->N    

Explanation:        

The reaction that eventually will prevail is the formation of the N molecule.

When Q and S are in high, they will inhibit the formation of P and R which are the molecules that form them. So, Eventually, there will not be P and R molecules, and hence, there will not be any more Q and S molecules.

L can still form equally M and N molecules. But as M forms O, and O inhibits M formation, with time, the higher O concentration is, the less M formation there will be.

On the other hand, N has no molecule that inhibits its production. So L turns to N formation, predominating this reaction.              

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link: