General ---------Biology----------------------------------------------------- ------------------Online--------------------------------------- Ch. 8 Membrane Structure and Function

Transmembrane or integral proteins function to relay chemical signals from one side of the membrane to the other.  These proteins are often called receptors and function in many of our senses, such as smell, taste, etc.  We studied such a protein in Ch. 2, the endorphin receptors located in the neural synapse.

Smell example:  Your nasal passages are lined with chemoreceptor cells containing a large number of receptor proteins, one for each smell you can recognize.  A rose flower gives off molecules that enter the active site of a receptor protein in your nose.  Once in the active site, the induced fit occurs, causing a change to the shape of the protein (a conformational change).  This relays the message to the inside of the cell.  The mechanism of the relay is usually the release of a chemical on the inside of the cell.  The receptor cell is adjacent to a nerve cell that is similarly stimulated and sends an electrical impulse to the portion of the brain responsible for creating the smell sensation.  The figure below, from Ch. 49 Sensory and Motor Mechanisms, of your text illustrates how these receptors work.

The image below locates this synapse and enlarges it to show how the signal hops across the synapse triggering the nerve cell impulse that travels to the brain.

This same mechanism is at work in sensations such as taste and in hormone activity and brain activity.