Cell Communication

A dense, sunlit outdoor crowd fills a riverside festival ground, with a stage and tents in the background and a bridge over water visible beyond them. — Have you ever become separated from a friend while in a crowd? If so, you know the challenge of searching for someone when surrounded by thousands of other people. If you and your friend have cell phones, your chances of finding each other are good. Cell phone networks use various methods of encoding to ensure that the signals reach their intended recipients without interference. Similarly, cells must communicate using specific signals and receptors to ensure that messages are clear. (credit: modification of work by Vincent and Bella Productions)

Imagine what life would be like if you and the people around you could not communicate. You would not be able to express your wishes to others, nor could you ask questions about your location. Social organization is dependent on communication between the individuals that comprise that society; without communication, society would fall apart.

As with people, it is vital for individual cells to be able to interact with their environment. This is true for both a one-celled organism growing in a puddle and a large animal living on a savanna. In order to properly respond to external stimuli, cells have developed complex mechanisms of communication that can receive a message, transfer the information across the plasma membrane, and then produce changes within the cell in response to the message.

In multicellular organisms, cells send and receive chemical messages constantly to coordinate the actions of distant organs, tissues, and cells. The ability to send messages quickly and efficiently enables cells to coordinate and fine-tune their functions.

While the necessity for cellular communication in larger organisms seems obvious, even single-celled organisms communicate with each other. Yeast cells signal each other to aid in finding other yeast cells for reproduction. Some forms of bacteria coordinate their actions in order to form large complexes called biofilms or to organize the production of toxins to remove competing organisms. The ability of cells to communicate through chemical signals originated in single cells and was essential for the evolution of multicellular organisms. The efficient and relatively error-free function of communication systems is vital for all life as we know it.

Sections

Signaling Molecules and Cellular Receptors — four types of cell-signaling mechanisms, how internal receptors compare with cell-surface receptors, and how a ligand’s structure relates to its mechanism of action.
Propagation of the Signal — how ligand binding initiates signal transduction, the role of phosphorylation in relaying intracellular signals, and the role of second messengers.
Response to the Signal — how signaling pathways direct protein expression, metabolism, and cell growth; the function of PKC; and the role of apoptosis in a healthy organism.
Signaling in Single-Celled Organisms — how single-celled yeasts signal one another, and how quorum sensing lets some bacteria form biofilms.

This chapter is adapted from Biology 2e, Chapter 9: Cell Communication by Mary Ann Clark, Jung Choi, Matthew Douglas, and OpenStax, © OpenStax, licensed under CC BY-NC-SA 4.0. Access the original for free at openstax.org. Each section page records its own changes from the source. Changes: the chapter-opening photograph is the source’s, re-encoded for the web with its credit kept in the caption and its alt text rewritten to describe the festival crowd and setting rather than restate the caption’s crowd-and-cell-phone analogy.

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