How do chemical messengers in the extracellular fluid bring about changes in cell function? Give an example of a chemical messenger for each mechanism noted.
Overall answers lacked structure and depth, to what is a very fundamental topic. This topic
is generally covered within the opening chapters of most physiology texts. Common errors
were not answering the question, writing lists rather than describing and explaining, and
poor categorisation. Candidates were expected to mention and give example for
mechanisms such as hormones binding to cytoplasmic or intra-nuclear receptors, binding to
transmembrane receptors coupled to G proteins, cAMP, cGMP, tyrosine kinase, etc.
Googling this question brings one to an online copy of Ganong (23rd ed.) where Table 3 from Chapter 2 has wording which spookily resembles the college question:
There's even examples. Sure, one could laizily copy and paste the whole table into the discussion section for this SAQ, as this author has done. An alternative would be to offer something which actually answers the question.
Chemical messengers in the extracellular fluid can affect cell function by:
Chemical cell signalling can be further subclassified:
Types of cell receptors for chemical messengers can be classified according to whether they are on the cell surface or intracellular:
Secondary messenger molecules are most easily classified according to their chemical characteristics:
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Bradshaw, Ralph A., and Edward A. Dennis. "Cell Signaling: Yesterday, Today, and Tomorrow." HandBook of Cell Signaling. Academic Press, 2010. 1-4.
Gao, Sizhi Paul, et al. "Mutations in the EGFR kinase domain mediate STAT3 activation via IL-6 production in human lung adenocarcinomas." The Journal of clinical investigation 117.12 (2007): 3846-3856.
Owen, Markus R., Jonathan A. Sherratt, and Simon R. Myers. "How far can a juxtacrine signal travel?." Proceedings of the Royal Society of London. Series B: Biological Sciences266.1419 (1999): 579-585.