Biology, Eighth Edition (Raven)

Chapter 46: The Endocrine System

Second Messenger: cAMP

Is ATP always used to provide energy for cellular work? Adenosine triphosphate (ATP) is an important molecule for a wide variety of cellular functions. Students usually first learn about it in the context of cellular respiration. ATP is vital for all life as a source of energy for transport, synthesis of macromolecules, muscle contractions, and a wide of variety of other tasks. However ATP serves other functions as well. ATP is also the source for cAMP, an important molecule in cell communication. Cleaving phosphates from ATP produces cAMP and produces the signal.

View the animation below, then complete the quiz to test your knowledge of the concept.


1.	The second messenger cAMP is synthesized by the enzyme

		A)	adenylyl cyclase.
		B)	cAMP phoshodiesterase.
		C)	ATPase.
		D)	ligase.
		E)	phosphorylase.

2.	The binding of epinephrine to its receptor activates a(n)

		A)	A protein.
		B)	D protein.
		C)	G protein.
		D)	K protein.
		E)	M protein.

3.	The enzyme α-kinase adds ________ to proteins.

		A)	acetates
		B)	benzoats
		C)	carbonates
		D)	phosphates
		E)	hydroxyls

4.	Epinephrine has to cross the cell membrane to bind to its receptor in the cytoplasm.

		A)	True
		B)	False

5.	The second messenger cAMP is made from ADP.

		A)	True
		B)	False