Lecture 5

Question 1

what are the 3 steps for the general model of cell signalling?

Answer 1

1) reception of a signal
2) transduction of a signal
3) cellular response

Question 2

describe the specificity of cell signal pathways?

Answer 2

individual cells respond to a certain set of signals for which they have receptors and different signals can act together to get different cellular responses (complex network)

Question 3

what is the difference between the way a signalling molecule works on different cell types?

Answer 3

the same signalling molecule may induce different responses in different cell types

Question 4

what are the 2 classes or extracellular signalling molecules and what receptors do they activate?

Answer 4

1) small hydrophobic molecules- activate intracellular receptors by passing directly through membrane
2) hydrophilic molecules - cant cross plasm membrane so rely on membrane receptors

Question 5

describe the closed loop control in signalling pathways?

Answer 5

Proteins produced from pathway which elicit response then feedback into the pathway

Question 6

what is the function of a signal cascade?

Answer 6

signal can be amplified then can split and diverge onto many targets

Question 7

what 2 things affect the impact and complexity of the signal?

Answer 7

1) number of receptors

2) speed of transduction

Question 8

what do receptor tyrosine kinases do?

Answer 8

enzyme linked receptor - they autophosphorylate themselves stimulating assembly of a signalling complex- complexes are disassembled by protein tyrosine phosphatases

Question 9

what are cytokines?

Answer 9

small secreted proteins which activate cells

Question 10

how do cytokine receptors act?

Answer 10

they signal to the nucleus in a direct pathway

Question 11

what is the importance of signalling and stem cells?

Answer 11

• stem cells are very sensitive to signals

- differentiate in different directions

Question 12

why does WNT signal have a different structure?

Answer 12

because it stops destruction rather than signalling activation

Question 13

why is balance important for TGFbeta and BMP signalling?

Answer 13

• when the ligands bind to the receptor TGFbeta produce SMAD2 and 3 and BMP produce SMAD1/5/8 which all compete for SMAD4
• therefore if one isn’t balanced it will override the other

Question 14

what does it mean signals are highly conserved?

Answer 14

there are only a few signals that can be used multiple times - its how they are used and in conjunction with each other which gives them different outcomes

Question 15

what are the 5 steps of signalling cascades?

Answer 15

1) transduce signal into another form that can stimulate response
2) relay signal from point of reception to point of action in the cell
3) amplify the received signal
4) distribute the signal to influence several responses in parallel
5) each step is open to modulation by other signals

Question 16

whats the difference between fast and slow extracellular signal pathways?

Answer 16

1) fast = altered protein function

2) slow = altered gene expression

Question 17

3 types of cell surface receptors?

Answer 17

1) ion channel linked receptor
2) g-protein linked receptor
3) enzyme linked receptor

Question 18

describe TGFB signalling?

Answer 18

transforming growth factor beta - important during development - exert anti-proliferative signals to cells - mutations in the pathway are associated with cancer

Question 19

what is the difference between notch signalling compared to WNT and BMP?

Answer 19

WNT and BMP = long range

Notch = works between adjacent cells - asymmetry