When does the phosphodiesterase that is required to deactivate cAMP exist in the cell?

a. It is synthesized in response to increasing cAMP concentrations.
b. It is actively absorbed from the intercellular medium by the cell.
c. Phosphodiesterase is always present in the cell.
d. Phosphodiesterase is a byproduct of cAMP hydrolysis.


c. Phosphodiesterase is always present in the cell.

Biology & Microbiology

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Several new tetraploid species of a plant called salsify (Tragopogon) known as salsify have arisen in western North America. These new species each arose from a diploid species that went through the process of allopolyploidy. This mode of speciation is a type of ________ and it occurs _______.  

A.  allopatric speciation; almost instantaneously B.  allopatric speciation; very slowly C.  sympatric speciation; almost instantaneously D.  sympatric speciation; very slowly E.  adaptive radiation; very slowly

Biology & Microbiology

In one minute, human DNA polymerase replicates about ________ bases.

A) 40 B) 100 C) 1,000 D) 3,000

Biology & Microbiology

Which of the following is made from tree bark?

a. cinnamon b. cocaine c. maple syrup d. hemp e. saffron

Biology & Microbiology

PCBs were frequently used in electrical transformers. A young man digs in an abandoned industrial site, finding old transformers, and sells the copper wire from them to a scrap yard. What health problems might the young man have in the future?

What will be an ideal response?

Biology & Microbiology