Cell signalling

Question 1

What is cell signalling? (5)

Answer 1

Ability to communicate between cells
Need to respond to the environment 
Quorum sensing
Respond to signals from other cells
Co-ordinate growth and development

Question 2

What are the 4 forms of intracellular signalling?

Answer 2

Contact dependent - membrane bound signalling molecule
Paracrine - signals released into extracellular space, act on neighbours
Synaptic - neurotransmitter
Endocrine - hormones released

Question 3

What is a ligand/agonist?

Answer 3

Binds to receptor and activates it

Question 4

What is an antagonist?

Answer 4

Binds to receptor and does not activate it

Question 5

What is a first messenger?

Answer 5

Ligand/agonist/hormone

Question 6

What is a second messenger?

Answer 6

Intracellular molecule produced in response to first messenger (Cyclic AMP)

Question 7

What is a signal transduction?

Answer 7

Process by which signal is transmitted into cell and then produce a final response

Question 8

Describe a simple signalling pathway: (4)

Answer 8

1. Signal molecule binds to receptor protein
2. Receptor activates 2nd messenger, signals a cascade
3. Signalling cascade influence traget protein
4. Signal transduction - alters gene expression

Question 9

How can you amplify a signal? (7)

Answer 9

Hormone –> receptor –> G-protein –> Effector –> 2nd messenger –> kinase –> phosphorylated enzyme

Question 10

What is cross talk?

Answer 10

Different signal transduction pathways may converge on a common target (enhance or attenuate response)

Question 11

What are the 2 types of first messengers?

Answer 11

Ligands:
Hydrophobic ligands (steroid hormones) permeable
Hydrophilic ligands (proteins) impermeable

Question 12

What are the 2 types of receptors?

Answer 12

Intracellular receptors

Cell-surface receptors

Question 13

What can cell surface receptors be bonded to for? (3)

Answer 13

Ion channels
G-protein coupled receptors
Enzyme coupled receptors

Question 14

How does an ion-channel coupled receptor work? (3)

Answer 14

Ligand binds to extracellular receptor
Channel opens to allow flow of ions
Change in cytoplasmic ion conc elicits cells response

Question 15

How do G protein coupled receptors work? (3)

Answer 15

Ligand binds to G protein
Activates intracellular G protein
Actives enzyme, changes conc of 2nd messenger

Question 16

How does an enzyme coupled receptor work? (3)

Answer 16

Ligand binds to cell surface receptor
Activation of enzyme activity of receptor
Recruitment and activation of intracellular enzyme

Question 17

What does a nuclear receptor do? (5)

Answer 17

Bind to ligand in the cytoplasm or nucleus
Loose an inhibitory protein 
Bind to a co-activator protein
Bind to specific DNA region 
Activates gene transcription

Question 18

How does the nuclear receptor work?

Answer 18

1. Inactive form receptor is bound to inhibitory protein complex
2. Ligand binding causes dislocation of inhibitory complex - stimulates gene transcription
3. Binding of ligand causes a conformational change in the receptor - allows coactivators to bind

Question 19

What is tamoxifen role on oestrogen?

Answer 19

Tamoxifen binds to estrogen receptor and blocks binding to coactivators