Chapter Eleven Reading Journal

Questions:

What are the three basic steps of Cell signaling?
Reception comes first when a chemical signal is detected by the cell this may happen because of direct contact or because the cell is receiving a signal that has already been passed along and is finally reaching the target cell. Transduction occurs when the message is converted so that it can be passed along to other signal molecules this is either done through the use of g-proteins, tyrosine kinasases, or ion channels. Response is when the cell behaves the way that the signal intended to make the cell.

How do G-Protein receptors work?
These receptor are in the membrane of cells and G proteins are either in the in active state of GDP or the active state of GTP when a phosphate has been added. When the g-protein receptor receives the signal molecule it changes the g-protein to the active form the g-protein then travels to an enzyme that it activates and often changes the shape of the enzyme once banded to it. This either immediately bringing about the cellular response or continuing to transfer the response through other enzymes. This is one of the most widespread cellular signaling functions.

What are Second Messengers?
Typically small water-soluble molecules or ions that are used to spread the signal within the cell. cAMP usually activates protein kinase A which typically spreads the signal by adding phosphorous to other proteins. This happens because the first signal that occurs in the membrane increases the levels of Camp to pass the signal along within the cell. Other cellular signals increase levels of ions most typically Ca + IP3 or DAG these work similarly to Camp in that the original signal triggers an increase in the ions which triggers further responses. Second messenger is a general term used for non-proteins used in the transductions pathways.

Facts:
- Cells have to communicate because they need to regulate cellular processes and respond to their environment as well as reproduce
- Cells perform apoptosis basically cell suicide when their DNA is coded improperly or they are about to stop functioning they do this to prevent damage to other cells
- Cell signaling can also stimulate certain genes within the nucleus to produce certain RNA
- Earl Sutherland discovered second messengers and the use of cAMp in epinephrine
- Ligands bind to receptors to promote the cellular response



This shows how signals can be transferred over a long distance. The original receptor activates a molecule that is able to activate other protein kinases. This works because a phosphate is added to the protein activating it then deactivates be transferring its P to another kinase, which is activated. Thus the reaction can move from molecule to molecule.

Summary:
Cell signals are either local or long distance. The main signal receptors are G-protein tyrosine kinnases and ion gated channels. To get from reception and response cells must undergo transduction pathways that either use phosphorylation cascade or secondary messengers. The response helps regulate transcription and other cellular functions this also helps them identify surrounding cells. The also use signaling to know when to self-destruct to prevent damage to nearby cells.