M&R 6.1 - Signal Transduction Flashcards
Describe paracrine signalling
A signalling molecule is produced by one cell and secreted into the tissue fluid where it can then act upon adjacent cells with the appropriate receptor
Describe endocrine signalling
A hormone is produced by an endocrine organ and travels in the circulation to a distant site where it acts upon its target cell
- Long distance
- Slower
- Specific
Describe synaptic signalling
- The release of a neurotransmitter by a nerve cell when stimulated to give a targeted response
- Signals are quick and long distance to specific target cells
Give an example of molecules that use paracrine signalling
- Local mediators e.g. growth factors
- Fibroblast Growth Factor (stimulate fibroblast proliferation and granulation tissue formation)
Give an example of a molecule that uses endocrine signalling
- Insulin
- Promotes glucose uptake in skeletal muscle/fat
- Inhibits glucose production by the liver
- Causes fat to be stored rather than used
Give an example of a molecule that uses synaptic transmission
- Acetylcholine
- Has many functions depending on which receptor is activated
Where are the receptors that are used by hydrophilic molecules located? Why are they here?
- On the cell surface membrane
- Hydrophilic molecules are unable to readily pass through the membrane
Where are the receptors that are used by hydrophobic molecules located? Why are they here?
- Intracellular receptors are used
- Hydrophobic molecules can readily pass through the membrane
What is the definition of a receptor?
A molecule that recognises a ligand/family of molecules and brings about the regulation of a cellular process in response
What is the definition of a ligand?
A molecule that binds specifically to a receptor site
What are the two types of ligand and what are their functions?
- Agonist = Activates receptor by causing a conformational change
- Antagonist = Combines to the receptor but doesn’t activate it therefore preventing binding of the agonist
Describe the affinity of receptors. What is the definition of Kd?
- Affinity of receptors is very high (higher than that of enzymes)
- Kd = Half of the concentration required to fill half of the receptors
What is the significance of a ligand binding to a receptor?
Brings about a change in response therefore controlling cellular processes
How are receptors classified?
- Initially into the type of agonist recognised
- Sub-classification = their affinity to antagonists (which is the most potent)
What is an acceptor?
A receptor like molecule that doesn’t need ligand binding to bring about a response