Cellular Signaling

Diagram showing the two forms of cell signaling: chemical signaling and receptor-mediated signaling.

Many living organisms contain billions of cells that carry out diverse functions. In order for the cells to cooperate, cells need to be able to communicate with each other. Many of the genes that cells are capable of synthesizing are thought to be involved in cellular signaling (a.k.a. signal transduction).

There are two methods of cell signaling: 1. cells secrete chemical signals that can be transported to distant cells. 2. that will enable them to communicate with other cells through physical contact.

Chemical Signaling

Chemical signaling can be classified into three categories: local-chemical mediator, hormone, and neurotransmitter. In the local-chemical mediator model, the secreted chemical acts on the cells in the immediate environment. Hormones are used for communication with distant target cells. For example, cells can secret a chemical and rely on the blood system to deliver the signal to a distant cell. Finally, neurotransmitters are secreted by neurons to stimulate an adjoining cell. For example, a neuron might secrete acetylcholine to stimulate the movement of a muscle cell.

Diagram showing the three different forms of chemical signaling: local chemical mediator, neurotransmitter, and hormone.

Receptor-Mediated Signaling

Cells also depend on direct interactions between surface receptors to communicate. Oftentimes, when the two cells bind together with their receptors and ligands, the shape of the receptor is changed and can induce the phosphorylation of an ADP molecule. This can then initiate a cascade of events.

Receptor-mediated signaling is also observed in the immune system. For example, white blood cells (T-lymphocytes) will bind to foreign proteins on a cell's surface when a cell has been infected. This binding-induced signaling will initiate a immune response.

Much research have been focused on different modes of cellular signaling. A better understanding of the different chemical signals and their associated-pathways can provide insights to cures for cancer, AIDS, and many other prominent diseases.

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