Tryptophan is an amino acid necessary for E. coli survival and growth. E. coli contain genes coding for enzymes that synthesize tryptophan. These genes are grouped together on a segment of DNA called the tryptophan (trp) operon. Cells can use these enzymes to synthesize tryptophan when it is not present in the environment. However, when tryptophan is already present in the environment, cellular resources are shifted away from manufacturing the enzymes for tryptophan synthesis. Tryptophan binds with and activates the trp repressor, which then binds to the trp promoter and blocks RNA polymerase. Blocking RNA polymerase decreases the normal transcription rate of the operon. The tryptophan (trp) operon consists of a promoter, an operator, and 5 trp genes. What type of regulation does the trp operon exhibit? protein modification positive regulation negative regulation translational regulation

Viruses are different from bacteria in that they can remain dormant on non-living surfaces they can be found just about anywhere they can infect just about every form of life

Consider the motion of the balloon and its air contents in terms of momentum. in step 1 above, the total momentum of the balloon and its contents was zero. recall that momentum = mv. both the balloon and the air inside it had a velocity of zero and therefore the total momentum was zero. now think about what happened when the air escaped from the balloon. a certain mass of air accelerated in one direction. in order to keep the total momentum of the system zero, the balloon itself (which has mass) had to accelerate in the opposite direction. use this scenario to you explain why the soda can rotates when the water squirts out of the escape holes. what was your hypothesis concerning the water-filled can? according to your data, do you think your hypothesis was correct? (be sure to refer to your data when answering this question.) summarize any difficulties or problems you had in performing the experiment that might have affected the results. describe how you might change the procedure to avoid these problems. give at least one more example of newton's third law in everyday life.

Which best describes the scientific method? a. a path of clearly defined steps that must be followed in a particular order b. a possible answer to a scientific question based on knowledge or research c. the recipe for how to conduct an experiment that must be followed precisely d. the process of hypothesis and testing through which scientific inquiry occurs