A phosphatase is capable of dephosphorylating molecules. What would this enzyme do in a signal transduction pathway that used a kinase cascade?
A. Serve as a ligand for the receptor.
B. Activate the cascade.
C. Turn off the cascade.
D. Phosphorylate a receptor.
E. Phosphorylate a transcription factor.
Answer: C
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Scientists have demonstrated that the cholera bacteria, Vibrio cholerae, can exist as a rather harmless form or, by phage conversion, can exist as a disease-causing, virulent form. This conversion is caused by
A. the phage entering the cholera bacterium genome and causing the bacterium's cell to lyse. B. the phage introducing a gene into the bacterium's chromosome that codes for the cholera toxin that can cause death in humans. C. the phage altering the cell wall of the cholera bacterium that produces a toxin that can cause death in humans. D. the phage alters the host cell, which permits direct entry of the cholera bacterium into the host cell leading to death in humans.
You look outside and realize that your grass needs to be mowed. You pick up the container of gasoline and see that you have approximately a third of a gallon left. You hypothesize that this amount will be enough to mow your entire lawn. Unfortunately, half way through mowing your lawn you run out of gasoline. You grumble and think to yourself that the next time you mow the lawn, you hypothesize that you will need to have at least two-thirds of a gallon of gasoline available. How did the results of your lawn-mowing experience influence the validity of your new hypothesis for future gasoline needs?
A. Your prediction proved that your hypothesis is correct. B. Your hypothesis was supported by trial and error. One more trial added to your data set. C. The hypothesis was invalidated by your experimental evidence. D. Your prediction of future gas needs is based on experimental data and therefore increases the validity of your hypothesis.
The cardiac conduction system initiates and delivers an electrical impulse that begins in the ________.
Fill in the blank(s) with the appropriate word(s).
Cells:
A) Work independently in the human body. B) are not the smallest structural units that perform all vital functions C) are organized into millions of different types in the human body D) do not exist as independent entities