High School Biology : Transport and Signaling

Study concepts, example questions & explanations for High School Biology

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Example Questions

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Example Question #5 : Understanding Second Messenger Systems

Which of the following is NOT an example of a second messenger?

Possible Answers:


All of these are second messengers.



Epinephrine (adrenaline)

Correct answer:

Epinephrine (adrenaline)


Second messengers are intracellular signaling molecules. Epinephrine is a hormone that is released into the bloodstream and is thus never inside the cell. cAMP, Ca2+ and IP3 are all examples of second messengers. They respond to primary messengers—which are often hormones—by amplifying their effects and/or turning on downstream effectors.

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