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Signal Amplification

How are signals amplified inside cells? A signal may reach a cell in the form of a single hormone molecule. Inside the cell, the signal must be amplified so that the response is carried out multiple times rather than just be a single molecule. Amplification is built into the system. Any molecule that catalyzes a reaction can do so multiple times producing more than one product molecule. So each step in the signaling chain has the potential for amplification. If a signaling chain is several steps long then there is a great potential for amplification of the signal. For example if the membrane receptor can produce 10 second messengers and each second messenger can generate the transcription of 10 mRNA chains then the signal has been amplified one thousand fold.

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






1An example of a second messenger is
A)AMP.
B)ATP.
C)cAMP.
D)cATP.
E)adenylyl cyclase.



2Arrange the following in the proper order in which they occur during signal amplification.

1. Activation of protein kinase
2. Activation of G protein
3. Activation of adenylyl cyclase
A)1, 2, 3
B)2, 1, 3
C)2, 3, 1
D)3, 2, 1
E)3, 1, 2



3Which of the following statements about signal amplification is TRUE?
A)A single cell surface receptor can activate only one G protein.
B)A single cell surface receptor can activate only two G proteins.
C)A single cell surface receptor can activate many G proteins.
D)It takes two cell surface receptors to activate a single G protein.
E)It takes many surface receptors to activate a single G protein.



4Most signaling molecules are found in low concentrations inside the cytoplasm.
A)True
B)False



5Cell surface receptors may be enzyme-linked or G protein-linked.
A)True
B)False







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