categories of chemical signalling found in multicellular  organisms

As discussed in your text book,  there are four categories of chemical signalling found in multicellular  organisms; paracrine signalling, endocrine signalling, autocrine  signalling and direct signalling across gap junctions. For this written  assignment     you will choose one of these signalling pathways to investigate in  more detail.

• Choose one out of paracrine  signalling, endocrine signalling, autocrine signalling and direct  signalling and describe briefly the process by which this occurs.
• Pick a representative signal  molecule from the pathway you have chosen and indicate its function,  the type of cell in which it is made and the specific manner in which it  acts as a signalling molecule, including the receptor that it binds to.

For example if you chose the  endocrine signalling pathway you could consider looking at a hormone  such as insulin.  You would describe the cells from which insulin is  secreted and state the overall role of insulin in the body.  In  signalling     pathways, each signal molecule has a receptor that it binds to, so  you would indicate what the receptor for insulin is called and what  immediate outcome the binding of insulin has to that receptor i.e.  in the case of insulin,     which regulates glucose uptake in the body, does the receptor  directly interact with glucose or is it just part of a much larger  signalling cascade.

KEGG PATHWAY Database

To give you an indication of the complexity of cell signalling, visit the KEGG (Kyoto Encyclopaedia of Genes and Genomes) PATHWAY database.  This database maps biological pathways     and displays them as a collection of diagrams or graphs.  If you wish to read more about it visit the overview page of the database.

• Open the KEGG PATHWAY Database  homepage. On this page, you can browse various types of pathways,  including metabolic and signalling pathways or you can search for terms  and find         the associated pathways.
• Using the search box, search for the molecule you have discussed above by entering its name.
• KEGG may give you the choice between several pathways, choose  one of these and click on the link under the heading ‘entry’. (this will  read something like map01578)
• Read the description of the pathway and write down its name then click on the image of the map.
• If possible copy the image of the map and insert it into your  written assignment, if this does not work for you provide a URL so that  the page can easily be accessed. The map consists of a set of rectangles  and circles which represent molecules, connected         by lines which indicate how these molecules interact or relate  with each other.  To understand how the information is organized on the  map, click on the “Help” button at the top left of the screen. You can  explore the map by clicking on its         individual elements and investigate the kinds of information is  available.
• Try to identify your chosen molecule on the map and make a note of the number and names of other molecules it directly interacts with in this pathway. If you are unable to identify your molecule of choice see if you can find its receptor, which         you identified earlier in this assignment.
• Click on the shape that contains your molecule of interest (or  its receptor) (this will redirect you to a page that lists the  signalling pathways in which that molecule is involved and any diseases  associated with it)
• Take a note of the names of at least three other pathways  indicated on this page and comment on whether your molecule is linked  with any diseases. (If there is no disease association there will be no  entry in the table)
• Review Endocrine Disruptors and  provide a brief overview of the mechanism of action of endocrine  disruptors. Comment on some of the effects of known endocrine         disruptors and suggest some steps that can be taken to reduce  the dangerous health effects posed by chemicals of this nature

Written Assignment Requirements

Your written assignment should be submitted in a Word document (or  similar program), double-spaced with 1-inch margins, and written in  Times New Roman size 12 font.  You should provide a word count at the  end of your written assignment.  Remember     to include APA formatted citations for all of the information you  have provided.
For help with APA citations