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Second Messengers - The cAMP and Ca++ Pathways

Why are calcium ions and cyclic AMP known as second messengers? Second messengers are small, non-protein molecules inside cells that relay a signal to the cell’s interior. The primary messenger is a signal protein that interacts with a receptor protein on the surface of the cell. The second messenger is the second molecule to carry the message. Calcium ions and cAMP are commonly used as second messengers for a variety of different signaling systems.

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






1The second messenger cAMP is synthesized by the enzyme
A)adenylyl cyclase.
B)cAMP phoshodiesterase.
C)ATPase.
D)ligase.
E)phosphorylase.



2Binding of a signal molecule to a cell surface receptor activates a ________, which in turn activates ________.
A)α-kinase ; phospholipase C
B)α-kinase ; adenylyl cyclase
C)α-kinase ; G-protein
D)G-protein ; α-kinase
E)G-protein ; phospholipase C



3Which of the following statements about inositol triphosphate is FALSE?
A)It is formed in the cytoplasm.
B)It is synthesized by a membrane-bound enzyme.
C)It is synthesized by the enzyme phosphatase.
D)It binds to and opens Ca2+ channels in the endoplasmic reticulum.
E)Choose this answer if all of the above are true



4Calcium ions serve as second messengers.
A)True
B)False



5The enzyme α-kinase adds phosphates to specific proteins.
A)True
B)False







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