Cell Signalling 1

Question 1

What are the 2 classes of extracellular signalling molecules?

Answer 1

1. Large and/or hydrophilic- bind to cell surface receptors
2. Small and/or hydrophobic- enter cell and bind to intraceullar receptors
   Most signalling molecules are hydrophilic.

Question 2

What is paracrine signalling ?

Answer 2

Released signal affects cells in close proximity.
Limited travel ability.
Eg. Some growth factors, histamine, nitric oxide

Question 3

What is autocrine signalling ?

Answer 3

Ligand is released from a cell then binds to a receptor on the same cell.
Eg. Molecules regulating development, some growth factors.

Question 4

What is endocrine signalling ?

Answer 4

Usually, the signal acts on distant cells (but can act on nearby cells).
Hormones
Eg. Insulin, adrenaline.

Question 5

What is juxtacrine signalling?

Answer 5

The signalling cell is in direct contact with the target cell.

Question 6

What is synaptic signalling ?

Answer 6

Axon of neurone transmits an electrical signal over long distances.
At axon terminal, electrical signal causes the release of NT into the synapse.
NT travels short distance only to specific target cell.

Question 7

What is signal transduction ?

Answer 7

Process whereby one type of signal is converted into another type

Question 8

How can the same signal molecule induce different responses in different target cells ?

Answer 8

Via:
1. Variants or isoforms of the same receptor
2. Similar receptors use different intraceullar signal transduction pathways

Question 9

What are common shape changes in signal transduction induced by ?

Answer 9

1. Molecules binding with each other
2. Addition/removal of a phosphate to the molecule
3. Molecule binds to a phosphate on another molecule

Question 10

What’s the point of a signal transduction cascade ?

Answer 10

1. Amplify the original signal
2. Integrate and distribute signals coming from other signal transduction pathways