[Campbell Biology P.210] Imagine a genetic mutation occurs in a cell that prevents isoleucin... | Practice Question

Imagine a genetic mutation occurs in a cell that prevents isoleucine from binding to the allosteric site of threonine deaminase Enzyme 1 in the isoleucine synthesis pathway. What would be the most likely long-term consequence for the cell?

  • A: The cell would produce isoleucine more rapidly, leading to increased cell growth and division.
  • B: The cell would be unable to synthesize isoleucine, leading to a severe deficiency of this amino acid.
  • C: The cell would continuously produce isoleucine even when sufficient amounts are present, leading to a wasteful expenditure of chemical resources.
  • D: The pathway would switch to producing a different, less essential amino acid instead of isoleucine.

Explanation

The text states that feedback inhibition 'prevents the cell from making more isoleucine than is necessary and thus wasting chemical resources.' If isoleucine cannot bind to its allosteric site on Enzyme 1, this regulatory mechanism fails. The cell would then continue to synthesize isoleucine unchecked, leading to an overabundance of the product and a depletion of the energy and precursor molecules needed for its synthesis, which constitutes a wasteful expenditure of resources.