Alumno

Biology



The Three Steps of Cell Signaling



1) Reception:

Target cell’s detection of a signaling molecule coming from outside the cell. Receptionof the signal depends on the receiver. A receptor protein on or in the target cell allows the cell to “hear” the signal and respond to it. The signaling molecule behavesas a ligand. Ligand binding causes a receptor protein to undergo a change in shape. This shape change activates the receptor enabling it to interact with cellularmolecules. The receptors in plasma membrane are G protein-coupled receptors, receptor tyrosine kinases and ion channel receptors. And the intracellular receptors are found in thenucleus and cytoplasm of target cells and are able to pass through the target’s cell plasma membrane.







2) Transduction:

This stage converts thesignal to a form that can bring about on a specific cellular response. Transduction sometimes occurs in a single step but more often requires a sequence of changes in aseries of different molecules – a signal transduction pathway. The molecules in the pathway are called relay molecules. The binding of a specific signaling molecule to areceptor in the plasma membrane triggers the first step in the chain of molecular interactions. Then a relay molecule activates protein kinase 1 and the phosphorylationprocess starts. Phosphorylation decreases the activity of the protein.




3) Response:

The transduced signal finally triggers a specific cellular response.The response may be almost any imaginable cellular activity. It may occur in the nucleus or the cytoplasm of the cell. Response helps regulate the activity of proteins.