Now that we’ve learned about cell communication, let’s the process of a single message as the cell passes it along:

We just watched how epinephrine is used as a sample messenger to trigger the release of glucose from cells in the liver. This is an example of phosphorylation, one of the two methods of intracellular signaling. The other method—second messengers—can be seen in Ca²⁺ signaling in muscle cells, which leads to muscle contractions.

These are just two examples of the many, many body functions that rely on cell communication. As we discussed in opening this module, imagine again what would happen if we could not communicate in society. Now, with your new appreciation of cell communication, imagine what would happen if even a single aspect of that process broke down.