Chapter 9: How Cells Communicate

1. Chapter 9: How Cells Communicate

2. This chapter discusses how cells receive and respond to signals from other cells. Multicellular organisms require specialized cells to perform the various processes of life efficiently. Specialization requires communication between cells. Cells use a variety of different signaling molecules to communicate with one another, including proteins, fatty acid derivatives, and even gases. To receive and interpret signals, cells have specific receptor proteins that bind signaling molecules and trigger certain chemical reactions inside the cell. Some receptor proteins reside in the cytosol and bind to signaling molecules that pass through the plasma membrane; others reside in the plasma membrane and bind only to external signaling molecules. One signaling molecule can induce many chemical reactions, amplifying the cell�s response to the signal. Different signaling molecules can affect some of the same chemical reactions in the cell, resulting in the combining of different signals.

3. Specialization and Communication in the Community of Cells The principle of cell specialization means that the cells found in a multicellular organism are not all the same, nor do they all have the same function. Specialized cells allow multicellular organisms to efficiently carry out processes necessary for life. Although cells are specialized, they do not operate in isolation. The lungs are a tissue that is made up of a number of specialized cells that work together to exchange carbon dioxide and oxygen (Figure 9.1). The second organizational principle that applies to all multicellular organisms is that of cell communication. Cells in a multicellular organism must communicate. The reflex of jerking away from a painful stimulus is an example of cell-to-cell communication between several different cell types (Figure 9.2). Communication between cells is accomplished with small proteins or other molecules that are released by one cell and received by another cell (target cell). �Signaling molecules� is a general term for the proteins and molecules used by cells for communication.