Please explain two mechanisms by which the presence or absen

Please explain two mechanisms by which the presence or absence of tryptophan regulates the activity of the trp operon.

Solution

If tryptophan is available in the environment, E. coli will take it up and use it to build proteins. However, E. coli can also make their own tryptophan using enzymes that are encoded by five genes (tryp E,D,C,B and A). These five genes are located next to each other in what is called the trp operon.

so In the presence of tryptophan bacterial cell have no need to prepare tryptophan for protein synthesis trytophan bind to tryp repressor and tryptophan repressor binds to tryptophan operator which stop the synthesis of trrptophan synthesis regulatory genes and hense stop the synthesis of tryptophan.

and in the abesence of tryptophan bacterial cell need to prepare pryptophan so

If there is no tryptophan in cell so it will not bind to tryp-repressor and it will to bindind of RNA polymerase to the promotor region which start the synthesis of trypophan synthesis regulatory gene