Answer: C). prolong the effect of epinephrine by maintaining elevated cAMP levels in the cytoplasm
Explanation: In the epinephrine pathway, binding of epinephrine to its receptor triggers a conformational change in the receptor and the interaction of the receptor with its associated Gs protein. This interaction causes the replacement of GDP bound to Gs protein with GTP thus activating the Gs protein. The activation of the Gs protein causes the alpha subunit of the Gs protein to dissociate and move to adenylyl cyclase, another membrane protein in the pathway. The association of the alpha subunit of the Gs protein with adenylyl cyclase activates adenylyl cyclase which in turn catalyzes the synthesis of cyclic AMP (cAMP) a second messenger. cAMP is quickly degraded to 5'-AMP by an enzyme phosphodiesterase. Inhibition of the activity of phosphodiesterase will increase the half life and the cytoplasmic level of cAMP thus potentiating the action of epinephrine.
Answer: D. The kinds of organisms that lived there long ago.
Explanation: Finding fossils in an area can help us learn about the kinds of organisms that lived there long ago. The fossil leave traces behind about what type of animal lived there and who the animal was.
