Lecture 01 - General Principles of Cell Communcation Flashcards
1
Q
What are the three types of cell signalling?
A
- Endocrine
- Paracrine
- Autocrine
2
Q
What is endocrine signalling?
A
- Secretion of a chemical messenger.
- Messenger is distributed systematically via the blood.
- Can affect cells far away from the gland.
- Hence, can affect large areas of the body.
3
Q
What is paracrine signalling?
A
- Involves secretion of a chemical messenger.
- Messenger diffuses to adjacent cells.
- Only affects cells at a short distance from gland because diffusion is a slow process.
4
Q
What is autocrine signalling?
A
- Involves secretion of a chemical messenger.
- The secretory cell and target cell are the same.
- Allows for a local response.
- Usually used to perform regulatory processes.
5
Q
What are the three stages of cell signalling?
A
- Reception
- Transduction
- Response
6
Q
What occurs in the process of reception?
A
- A chemical messenger binds to a protein on the cell surface.
7
Q
What does the process of transduction involve?
A
- The binding of the signal molecule alters the receptor protein.
- Signal molecule usually starts a cascade of reactions known as a signal transduction pathway.
8
Q
What does the process of response involve?
A
- Transduction pathway triggers a response.
- Responses vary from:
Turning on a gene
Activating an enzyme
Rearranging the cytoskeleton - Usually an amplification of the signal occurs.
One hormone can elicit response of >10^8 molecules
9
Q
What are receptors?
A
- Receptors are present on the cell membrane of responsive cells.
- The cells express appropriate receptors which recognise the messenger.
- Allows for a response, via a biochemical or physiological change.
10
Q
What are three types of receptor?
A
- Receptor tyrosine kinase (RTK)
- Ligand gated ion channels
- G-protein coupled receptors (GPCRs)
11
Q
How does a RTK receptor work?
A
- A receptor tyrosine kinase responds to growth factor.
- If defective, it may lead to uncontrolled growth, and cancer.
Works:
3. 1st messenger binds to the receptor.
- The binding causes dimerisation.
- Dimerisation causes enzyme activation (tyrosine kinases).
- Enzyme activation causes phosphorylation of the receptors.
- Phosphorylation leads to a cellular response as proteins are activated.
12
Q
How does a ligand gated ion channel receptor work?
A
- 1st messenger binds to the receptor.
- Binding causes the channel to open.
- Opening of channel allows ions to flow through.
13
Q
What is an example of a ligand gated ion channel?
A
- Nicotinic acetylcholine receptor (NachR).
- This receptor is a 4-5 subunit quaternary protein.
- Protein allows for a specific ion to flow through, Na.
14
Q
How does NachR work?
A
- Hydrophobic interactions cause the channel to remain closed.
- Acetylcholine, an agonist, binds.
- Binding causes a breakdown of the hydrophobic interactions.
- Breakdown causes the pore to open.
- Opening means Na ions can diffuse through.
- However, mutations will cause continual activity = receptor will be signalled even when no ligands are present.
15
Q
How do GPCRs work?
A
- 1st messenger binds to the receptor.
- Binding activated the coupled receptor, the G-protein.
- G-protein transduces signal to the effector.
- Effector causes a conformational/biochemical change.
