General principles of cell communication

Question 1

What are the three areas of cell signalling?

Answer 1

• Endocrine- this involves secretions of chemical messenger. This is distributed systemically and can affect cells at some distance form the gland. As a result, this affects large areas of the body
• Paracrine- this involves a secretion of a chemical messenger. This diffuses into adjacet cells and only affect cells at a short distance as diffusion is slow
• Autocrine- the seceretory cell and target in this case are the same. This allows for a very local response, in order to perfor regulatory processes

Question 2

What are the stages of cell signalling?

Answer 2

• Reception- a chemical message binds to a protein on the cell surface
• Transduction- the binding of the signal molecue alters the receptor proten in some way. The signal ususally starts a cascade of reactions known as a signal transduction pathway
• Response- the transduction patheay finally triggers a response. The responses can vary from turning on a gene, activiating an enzyme, rearranging the cytoskeleton.

Question 3

What are the three types of cell receptors?

Answer 3

1. Receptor Tyrosine Kinase RTK
2. Ligand gated ion channels
3. G protein coupled receptors

Question 4

How does RTK work

Answer 4

This receptor responds to growth factor. If defective, it may lead to uncontrolled growth, cancer

The receptor works in the following way

1. 1st messenger binds to receptor
2. causes dimerization
3. enzyme activated
4. allows for phosphorylation
5. activates proteins- > cellular response

Question 5

How does ligand gated ion chanel work?

Answer 5

1. 1st messenger binds to receptor
2. causes the channel to open
3. allows ions to flow through

Example Nicotinic acetylcholine receptor

• 4-5 subunit quaternary protein
• allows a specific ion to flow through- Na

1. Hydrophobuc interactions cause closed channel
2. ACh agonist binds
3. causes a breakdown of hydrophobic interactions
4. causes the pore to open
5. Na can diffuse through

Question 6

How does GPCRs work?

Answer 6

1. 1s messenger binds to receptor
2. activates GPCR
3. transduces sugal to effector
4. effector causes a cnformatiobiochemical change

Example- muscuranic acetylcholine receptor

1. Muscarin mimics ACh
2. blocks the receptor
3. prevents signalling
4. causes pupil dilation