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

Wars Essay Example | Topics and Well Written Essays - 1000 words

Wars - Essay Example tion of the US to Somali, though there is no clear evidence of the fact that the terrorist organizations responsible for the biggest world terrorist acts take their places in either of the countries. On the contrary, the intervention to these countries has caused chaos and disorder. This statement can possibly be denied by the explanation that the war was not the absolutely desirable way out to stabilize situation in the country, and was actually aimed at creating new society with democratic values, but the fact that presence of the terrorist organizations was only suspicion, and it is yet not understood, after so many years of war, whether this war was the best solution for the problems which existed between the two countries. It has caused deaths of thousands people of the common population but has not yet reached its goal of destroying terrorist groups. Thus, suspicion is not enough to start and hold wars. Thus, we come to another argument against wars – innocent people mos tly become the victims of the political games, which often turn into wars. Modern times represent us with the new kinds of wars, which countries and peoples can have against each other, starting from physical (military), and ending with the informational and oil (gas) wars. The issue of the innocent people is more related to the fact when one speaks about military actions. ‘While the image of bombers flying over Afghanistan and bombing a people whose average lifespan is about 45 years of age and who are suffering terrible deprivation already -- not least due to the Taliban, which the U.S. helped create and empower -- is horrifying enough, it is important to realize that death and deprivation come in many forms. Even without widespread bombing, if the threat to attack the civilian population or outright coercion of other countries leads to curtailment of food aid to Afghanistan, the ensuing starvation could kill a million or more Afghans by mid-winter. Is this the appropriate response to