Cell Biology Essay Example | Topics and Well Written Essays - 500 words - 1

Cell Biology - Essay Example downregulate the expression of the histidine biosynthetic enzymes in the presence of ample histidine, since the cell does not need to synthesis histidine under those conditions. If HisP functions as a gene activator, I would expect it to bind more tightly to the regulatory sequences under conditions with low levels of histidine. As a gene activator, HisP would function to increase the expression of genes necessary for the biosynthesis of histidine. This would be more necessary and beneficial to the cell under conditions of low histidine. 2. In class we talked about how bacterial cells can take up the amino acid tryptophan from their surroundings, or if the external supply is insufficient, they can synthesize trytophan by using enzymes in the cell. In some bacteria, the control of glutamine synthesis is similar to that of tryptophan synthesis, such that the glutamine repressor is used to inhibit the transcription of the glutamine operon, which contains the genes that code for the enzymes required for glutamine synthesis. Upon binding to cellular glutamine, the glutamine repressor binds to the site of the promoter of the operon. By repressing the expression of the glutamine operon in the abundance of glutamine, as when the repressor molecule is bound to glutamine, the cell can conserve energy by not synthesizing a molecule that is already in abundance in its environment. When the supply of glutamine drops, the number of repressor molecules bound to glutamine, and hence repressing the expression of the glutamine operon, drops as well. This allows the cell to express the glutamine operon in order to raise levels of glutamine through its own biosynthetic pathway. The regulatory mechanism would fail because no allosteric (or other) changes induced by glutamine binding to the repressor molecule would allow it to bind to the glutamine operon promoter and cease synthesis of it. As a result, assuming no other regulatory mechanisms prevented it, the cell would