[Animation] - Membrane-Bound Receptors, G Proteins, and Ca2+ Channels

How can one type of signal produce different responses in different cells?

Cell signaling pathways have many elements in common. G proteins and calcium channels are used in a number of different cell types to produce different responses. How is this possible? Different types of cells have different receptor proteins on their membranes. A liver cell will have different receptors from a muscle cell, for example. A liver cell will not respond to a ligand (external signal molecule) for a muscle cell because it lacks the appropriate receptor molecule. Even though other aspects of cell signaling may be similar in the two cells they can produce completely different reactions because the initial receptor molecule is different.

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