Cell signalling

Question 1

What are the types of cell signalling?

Answer 1

Synaptic
Endocrine
Autocrine
Paracrine

Question 2

What can signalling molecules be made of?

Answer 2

Proteins
Amino acid derivatives
Nucleotides
Steroids
Retinoids
Fatty acid derivatives
Dissolved gases

Question 3

Do hydrophobic molecules diffuse through the cell membrane? Where do they bind to receptors?

Answer 3

Yes
Bind to intracellular receptors

Question 4

Do hydrophilic molecules diffuse through the cell membrane?

Answer 4

No - they bind to extracellular receptors which pass the message on intracellularly

Question 5

What are the types of cell surface receptors?

Answer 5

Chemically gated channel
Enzyme
GPCR

Question 6

What are the steps of the GPCR cascade?

Answer 6

1. extracellular signalling molecule binds with GPCR and undergoes conformational change
2. G protein binds with bound GDP on alpha subunit
3. GDP dissociates, replaced by GTP and alpha subunit diffuses away to AC (enzyme), leaving GCPR and beta/gamma subunits
4. AC activated and synthesises cAMP
5. Protein Kinase activated by increase in cAMP concentration

Question 7

What is the purpose of secondary messengers?

Answer 7

Amplify the signal

Question 8

What is cross talk and how can it affect signal transduction?

Answer 8

Inputs from several signalling pathways
If using the same secondary messengers, can reduce signal due to concentration

Question 9

What is a common way for secondary messengers to transfer information?

Answer 9

Protein phosphorylation - causes conformational change, alter enzyme activity

Question 10

Give an example of how different cells can respond differently to the same molecule

Answer 10

PKA - in adipocytes stimulates lipase, in myocytes it stimulates glycogen synthesis

Question 11

How is a signal terminated? Give an example

Answer 11

Reversal of the reaction via negative feedback
e.g. shut off phototransduction in the retina