"tryptophan self-controls its synthesis." justify this statement.

if a lesser amount of tryptophan is present in a cell, tryptophan acts as an inducer and binds to a repressor, leading to the synthesis of enzymes required for its production and thus its synthesis.

if an excess amount of tryptophan is present in a cell, tryptophan acts as a promoter, preventing the further synthesis of necessary enzymes for its production and thus its synthesis.

if an excess amount of tryptophan is present in a cell, tryptophan acts as a co-repressor, preventing the further synthesis of necessary enzymes for its production and thus its synthesis