Final answer:
The level of cyclic adenosine decreases when the level of glucose in the environment is low. This is because cyclic adenosine is used as a second messenger to stimulate glucose release when glucose levels are low.
Step-by-step explanation:
The statement contains inaccuracies. First, it refers to "cyclic adenosine," but the correct term is "cyclic adenosine monophosphate" or cAMP. Second, it states that glucagon activates adenylyl cyclase, which is correct. However, it suggests that cAMP decreases when glucose levels are low, which is not accurate.
In response to low glucose levels, glucagon activates adenylyl cyclase, leading to an increase in cAMP levels. Elevated cAMP, in turn, activates protein kinase A (PKA) and other signaling pathways, promoting processes that raise blood glucose levels, such as glycogenolysis and gluconeogenesis. Therefore, when glucose is low, cAMP levels rise as part of the cellular response to mobilize glucose and maintain energy homeostasis.