LIFE 102 Lecture Notes - Molecular Switch, Cyclic Adenosine Monophosphate, Cell Membrane
Document Summary
Protein phosphatases remove the phosphates from proteins, a process called dephosphorylation. This phosphorylation and dephosphorylation system acts as a molecular switch, turning activities on and off. The extracellular signal molecule that binds to the receptor is a pathway"s first messenger . Second messengers are small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion. Second messengers participate in pathways initiated by g protein-coupled receptors and receptor tyrosine kinases. Cyclic amp and calcium ions are common second messengers. Cyclic amp (camp) is one of the most widely used second messengers. Adenylyl cyclase, an enzyme in the plasma membrane, converts atp to camp in response to an extracellular signal. Other components of camp pathways are g proteins, g protein-coupled receptors, and protein kinases camp usually activates protein kinase a, which phosphorylates various other proteins. Further regulation of cell metabolism is provided by g-protein systems that inhibit adenylyl cycles. Calcium ions (ca2+) act as a second messenger in many pathways.
