Signal trsnduction

Signal trsnduction - C H A P T E R 9 SIGNAL TRANSDUCTION...

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123 C H A P T E R 9 SIGNAL TRANSDUCTION PATHWAYS Signal Transduction Pathways Organization Signals Receptors Soluble Receptors Transmembrane Receptors Enzyme Coupled Receptors G-Protein Coupled Receptors Ion-Channel Coupled Receptors Second Messengers Amplifiers Integrators Inhibitors SIGNAL TRANSDUCTION PATHWAYS Allow the cell to sense and respond to signals in the environment. Signal R Receptor R Transducer R Effector R Response. upstream R downstream
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124 Basic Concepts in Biochemistry Signal transduction pathways allow cells to respond to their environment and to change their behavior accordingly. Signals are sensed by a recep- tor and changed in their form (transduced) so that they can exert their final effect on the cell. In addition to the straightforward chain of events that may lead from a signal to a final effect, there are components of these pathways that are designed to amplify and integrate various cellu- lar responses. This leads to a bewildering array of biochemical interac- tions with branches leading off in all directions, feedback loops (that use the final effect to turn down the original response), and a series of inhibitors and activators that may activate multiple pathways at the same time. The best approach for dealing with signal transduction pathways (as always, in my opinion) is to learn the various kinds of general pathways that exist and then try to fit new pathways onto these types. There are a few general principles of signal transduction pathways that can be used to organize your approach. ORGANIZATION Components of signal transduction pathways are similar—what dif- fers is the details (Fig. 9-1). Receptor Signal Activated receptor Second messenger Effect Effector Transduction pathway Figure 9-1 Generalized Signal Transduction Pathway
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9 Signal Transduction Pathways 125 Signals: start the whole thing. They’re what the target cell senses. Receptors: sense the signal and are activated. Sensing the signal causes a change in the structure of the receptor. This structural change acti- vates the pathway. Transducers: receive the signal and then pass it on in a different form. They can amplify the signal or integrate signals from multiple path- ways. Most components of signal transduction pathways can be con- sidered transducers. Second messengers: small molecules that are released in the cell in response to a signal. They can activate many other downstream com- ponents. Amplifiers: increase the strength of the signal. They turn one molecule of original signal into many, many molecules of second messengers or secondary signals. Integrators: allow multiple signals to converge on a single response. Effectors: the final step of the signaling pathway. Their activation results in the effect. Sometimes signals can activate multiple path- ways and have multiple effects.
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This note was uploaded on 04/09/2008 for the course BIO SCI 98 taught by Professor Goulding during the Spring '08 term at UC Irvine.

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Signal trsnduction - C H A P T E R 9 SIGNAL TRANSDUCTION...

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