Signaling Molecules: Definition & Concept Video

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  • 0:00 What Are Signaling Molecules?
  • 1:01 Process
  • 2:33 Types
  • 3:59 Lesson Summary
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Lesson Transcript
Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

How do cells know which processes and activities to perform? In this lesson, you will learn about the ways that cells receive information and how that information gets translated into a message that the cell can understand.

‚Äč!!!What Are Signaling Molecules?

Have you ever played a game of telephone? This game involves transmitting information down a line of messengers, though the message often gets a bit convoluted by the end. Because it's a game, it's fun to see how the message gets distorted by the end of the line.

Your body functions in a similar way when messages need to be conveyed from one part to another. For example, your eyes are sending messages to your brain right now as you read this, and your brain is sending messages back to your eyes, as well as other parts of your body. Unlike the telephone game, though, it's essential that these messages be conveyed correctly!

Signaling molecules are the molecules that are responsible for transmitting information between cells in your body. The size, shape, and function of different types of signaling molecules can vary greatly. Some carry signals over short distances, while others transmit information over very long distances.


All signaling molecules carry messages, but this is just one step in a larger process. Something must also receive this message and decode it for the receiving cell. This process of cell signaling is divided into three stages: signal reception, signal transduction, and cellular response.

The first step, signal reception, is when the signaling molecule encounters a receptor. In the telephone game, this would be the person receiving your message. This step often occurs on the outside of the cell at the plasma membrane. A chemical signal is detected when the signaling molecule binds to the receptor, which changes the receptor's shape and triggers the second step of the process.

The transduction stage converts the received signal to a form that is more understandable by the cell, which allows the cell to respond appropriately. This stage is like a translation of the message from the signaling molecule to the cell. Transduction sometimes occurs as a single step but more often requires a sequence of changes called a signal transduction pathway. The molecules in the pathway are called relay molecules, and each is modified as the signal moves down the pathway.

In the final stage, called response, the transduced signal finally triggers a specific response in the cell. The response may be almost any imaginable cellular activity, but most importantly it ensures that the activities and processes occurring are happening in the correct cells at the correct time.


There are four main types of signaling molecules, let's look at each a little more closely:

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