Signal Transduction

Question 1

What is signal transduction?

Answer 1

Process of converting an extracellular signal into an intracellular response

Question 2

Where do signals come from?

Answer 2

Can be produced by signalling cells in an organism, or from the environment

Question 3

How are signal transduction and cell differentiation?

Answer 3

Cells will respond to a series of differentiation signals and activate specific pathways to become a particular cell type

Question 4

What determines how a cell will respond to a signal?

Answer 4

What cellular machinery it has present when it receives the signal. Like it doesn’t matter how much EGF you dump on a cell, it won’t respond if it isn’t expressing a receptor for it

Question 5

What are slow response pathways?

Answer 5

The cellular response is gene expression, which takes a while

Question 6

What are fast response pathways?

Answer 6

The cellular response alters proteins already there and changes their function, which is faster

Question 7

What is contact dependent signalling?

Answer 7

The signalling cell has the signal stuck to its surface, and the signal stays stuck. The receiving cell with the receptors has to make physical contact with the signalling cell for it to do anything

Question 8

Where do we see contact dependent signalling?

Answer 8

During development and in immune responses

Question 9

What is paracrine signalling?

Answer 9

The signalling molecule is secreted by the signalling cell, but it only acts on nearby cells and doesn’t go very far

Question 10

What stops paracrine signals from diffusing too far away from their targets?

Answer 10

They’ll be immobilized, degraded, or sequestered

Question 11

What is endocrine signalling?

Answer 11

The signalling molecule is secreted by the signalling cell and enters the bloodstream where it acts on things far away from the original source

Question 12

What are the 4 general steps of a signalling pathway?

Answer 12

1. Ligand binds
2. Receptor and intracellular effector proteins become activated
3. Cellular response
4. Deactivation of the pathway

Question 13

Where will be the receptor for a hydrophilic signalling molecule?

Answer 13

Cell surface

Question 14

Where will be the receptor for a hydrophobic signalling molecule?

Answer 14

Inside the cell

Question 15

Why are signalling pathways so fast?

Answer 15

Everything is already present and in place when the signal binds

Question 16

What is signal integration?

Answer 16

Cross talk between different activated pathways that coordinate the cellular response

Question 17

What are 5 common components of signalling pathways?

Answer 17

1. Receptors
2. G proteins
3. Protein kinases and phosphatases
4. Intracellular secondary messengers
5. Activation of transcription factors and altered gene expression (for slow response pathways)

Question 18

How can you study if a pathway is being activated?

Answer 18

In vitro kinase assays. Use antibodies that recognize the phosphorylated protein and do a western blot