Question

An amino acid is synthesized by the prokaryote, E coli. The genes for the enzymes responsible for synthesizing this amino acid are encoded in an operon. The operon is regulated by a repressor. When the amino acid binds to the repressor, the repressor changes shape so it can bind to the operator. Which of the following statements is true?
A) When levels of the amino acid are high, it binds to the repressor, allowing synthesis of this amino acid to proceed.
B) When levels of the amino acid are low, it binds to the repressor, allowing synthesis of this amino acid to proceed...

Answer 1

The statement "When levels of the amino acid are high, it binds to the repressor, allowing synthesis of this amino acid to proceed" (A).

E. coli needs amino acids to survive. It can ingest the amino acid, Tryptophan from the environment. When the levels of Tryptophan are low, it can synthesize Tryptophan by using enzymes that are encoded in five genes. These genes lie next to each other in the tryptophan operon. If tryptophan is available in the environment, E. coli will not synthesize it.