Cell signalling

Question 1

What can cell signalling cause?

Answer 1

Cell division
Cell growth
Differentiation 
Cell movement
Cell death

Question 2

What are the cellular responses to signalling + examples

Answer 2

Change in metabolic activity - glucagon switches liver from synthesising glycogen to metabolising
Secreting/release - binding of antigen causes mast cells to secrete histamine
Changed gene expression - epidermal growth factor (EGF) activates genes involved in cell growth
Sensory perception - light activation of rhodopsin

Question 3

What can act as extracellular signals + examples?

Answer 3

Amino acids + derivatives = glutamate, adrenaline, dopamine
Steroids = oestradiol, testosterone, cortisol, aldosterone
Prostaglandins (eicosanoids, derived from arachadonic acid)
Proteins + peptides = insulin , glucagon, growth factors EGF
Gases = NO, CO

Question 4

What amino acids + derivatives can act as extracellular signals?

Answer 4

Glutamate
Adrenaline
Dopamine

Question 5

What steroids can act as extracellular signals?

Answer 5

Oestradiol
Testosterone
Cortisone
Aldosterone

Question 6

What are prostaglandins?

Answer 6

Eicosanoids, derivatives of arachadonic acid.

Question 7

What proteins/peptides can act as extracellular signals?

Answer 7

Insulin, glucagon, growth factors, EGF

Question 8

What gases can act as extracellular signals?

Answer 8

NO, CO

Question 9

What are they ways in which cells can signal each other?

Answer 9

Paracrine
Autocrine
Contact-dependent
Endocrine
Neuronal
(PACEN)

Question 10

What is paracrine signalling

Answer 10

Signal produced by cell close by

Question 11

What is autocrine signalling

Answer 11

Signal produced by cell itself

Question 12

What is endocrine signalling

Answer 12

Signal produced in one part of the body, and then travels in the blood and acts elsewhere

Question 13

What is contact dependent signalling

Answer 13

Signal is integral part of one cell which interacts directly with another cell

Question 14

What is neuronal signalling

Answer 14

Electrical signal sent down a cell, passed on via synapse

Question 15

What are the two types of receptor and what type of signalling substances do they respond to?

Answer 15

Cell surface receptor - hydrophilic substances such as adrenaline. The signalling hormone does not enter the cell.
Intracellular receptor - hydrophobic substances such as steroid hormones. Hormone crosses the membrane and enters cytosol to trigger a response inside the cell.

Question 16

What can signalling cause within a cell

Answer 16

Depolarisation of membrane due to the flow of ions (acetlycholine)
Direct activation of transcription factor (steroid)
Production of secondary messenger (cAMP)
Direct activation of enzymatic kinase cascade (EGF - MAPkinase pathway)

Question 17

Example of signalling causing depolarisation of membrane due to flow of ions

Answer 17

Acetylcholine binding to nicotinic acetylchloline receptor

Question 18

Example of signalling causing the direct activation of transcription factors

Answer 18

Binding of steroid induces a conformational change which allows DNA binding + activation of transcription of target genes.

Question 19

Examples of secondary messengers

Answer 19

cAMP
cGMP
Ca2+
IP3
DAG

Question 20

IP3

Answer 20

Inositol-1,4,5-trisphosphate

Question 21

DAG

Answer 21

Diacylglycerol

Question 22

What does GPCR stand for?

Answer 22

G-protein coupled receptor

Question 23

Give an example of a GPCR

Answer 23

Beta-adrenergic receptor

Question 24

How can stimulation of the Beta-adrenergic receptor lead to the production of cAMP?

Answer 24

Stimulation of GPCR B-adrenergic receptor by adrenaline activates a G-protein.
The as subunit swaps GDP for GTP then dissociates from beta and gamma units to activate the adenylyl cyclase; which produces cAMP.
GTP hydrolysed to GDP as as-b-y complex re-associates, signalling ends.

Question 25

How does cAMP activate PKA

Answer 25

``` Inactive PKA (protein kinase A) is made up of 4 monomers: 2 regulatory subunits and 2 catalytic subunits. 2 molecules of cAMP bind to the regulatory subunits and releases the catalytic subunits, activating it. ```

Question 26

How can cAMP affect gene transcription?

Answer 26

It activates CREB (cAMP response element binding protein); which binds to specific genes, stimulates transcription Then long term adaptation to starvation to change in gene expression.

Question 27

What is CREB

Answer 27

cAMP response element binding protein

Question 28

How can GPCR be involved with IP3 and DAG in activation of PKC

Answer 28

GPCR (in alpha1-adrenergic receptors) can have a G-alpha-q / Gq subunit; which activates phospholipase C Phospholipase C cleaves inositol phospholipids- producing inositol-1,4,5-trisphosphate and diacylglycerol. IP3 activates Ca2+ channel in ER and so increases cytoplasmic [Ca2+], this alongside DAG can activate PKC.

Question 29

What is RTK

Answer 29

Receptor tyrosine kinase

Question 30

What does RTK do

Answer 30

Causes direct activation of enzymatic kinase cascade without a secondary messenger. Binding of EGF triggers autophosphorylation of tyrosine residues in cytoplasmic domain of receptor. Activates exchange of GDP-Ras to GTP-Ras Ras is a G-protein that triggers a kinase cascade

Question 31

What does Ras do

Answer 31

Its a G-protein that triggers a kinase cascade; MAPKKK-MAPKK-MAPk-transcription factor (mitogen activated protein kinase ...) No secondary messenger

Question 32

What is convergence in terms of intracellular signalling?

Answer 32

When two different signals cause the same effect in a cell

Question 33

What is crosstalk in terms of intracellular signalling?

Answer 33

When two signals block each other (dimmer switch analogy)