Blog 3.D

3. D. 1

1. Explain what factors are involved in cell communication.

Signal transduction: reception, transduction, response.

2. Explain why signal transduction process are generally under strong selective pressures. They need to tell the cell to do something and if the cell doesn’t or of the ligand signals the wrong cell to do the wrong thing then it could cause maaajor complications.

3. Explain how signal transduction pathways influence how the cell responds to the environment using Quorum Sensing as an example.

Cells send out signals via ligands which bind to receptors on the outside of the destined cell. These signals tell the cell what to do. Quorum sensing is used to sense how many bacteria are in the cell’s environment. Based on this, the cell will replicate, not replicate, or to or not to perform certain cell processes like attack a host or glow. One bacteria by itself or in a small group will hardly affect an organism but a significant number of bacteria could have a huge effect on it.

4. Why is signal transduction important? It is important because cells need to be able to communicate and respond to either their own or extracellular signals to keep themselves alive, their organism alive and more.

3.D.2

1. Explain cell to cell contact communication and give an example.
Contact-dependent signaling- an example is killer T cells destroying infected cells.

2. Explain cell communication over short distances and give an example.
This is called paracrine signaling and an example is neural signals, which leave the axon, hop a gap and enter the next dendrite through receptors on that dendrite. 

3. Explain cell communication when signals travel over a long distance and give an example.
This is called endocrine signaling and an example would be the adrenal glands sending adrenaline to the legs in preparation for a flight reaction.

3.D.3

1. How does signaling begin in a signal transduction pathway? It begins by a ligand attaching to a receptor.

2. Explain the ligand receptor relationship. What does it initiate?
The ligand-receptor relationship is the receptor on the cell’s exterior which binds to certain ligands, which are protein signals. It releases GDP which goes on to a few more processes and ultimately amplifies the ligand’s signal. It causes the cell to respond, also.

3. Explain a G protein linked receptor. It is linked to the receptor and when a ligand binds to it the G protein (GDP) turns into GTP and goes on to trigger other things like cAMP and amplifies the signal. 

4. Explain a ligand gated ion channel.
These need proteins (like sodium) to hook on and open the channel so ligands can pass through.

5. Explain receptor tyrosine kinases.

RTK: growth factor – binds and activates receptor/dimer – fills with phosphates- tyrosine- sends out signals to muscles etc

6. Signal transduction is the process by which a signal is converted to a cell response. Explain the entire process of signal transduction. Use the following terms (ligand, receptor, protein kinase, secondary messenger, phosphorylation, transduction, cell response)

The ligand- einepherine, for example, binds to a receptor which changes its shape and releases G protein, changing it to GTP. It goes to Adenolate cyclase makes cAMP – phosphorylation cascade amplifies the signal, which is to have the cells turn glycogen to glucose

3.D.4

1. Conditions where signal transduction is blocked or defective can alter cell response. Give an example of when this occurs. What happens?
Well, if the signal transduction pathway is blocked the effects are usually harmful to the cell. AN example would be how cholera secretes toxins that tell the cells to send water to the intestines, which causes excessive diarrhea and dehydrates the body/cells. It modifies the G protein so it can’t go back to GDP and the cells can’t stop signaling the water to quit going to the intestines.

Citations:

http://upload.wikimedia.org/wikipedia/commons/a/a4/1Signal_Transduction_Pathways_Model.jpg

http://www.scq.ubc.ca/conversing-at-the-cellular-level-an-introduction-to-signal-transduction/
http://www.ebi.ac.uk/interpro/potm/2005_9/Page2_files/image004.jpg