Intracellular Communication

Question 1

What is an activation signal in terms of feedback loops

Answer 1

Positive feedback loop- amplifying signal
Negative feedback loop- help control output of the system

Question 2

What are the four main types of intercellular signalling

Answer 2

-contact dependent
-paracrine
-synaptic
-endocrine

Question 3

Outline contact dependent signalling

Answer 3

Extracellular signal molecules remain bound to the surface of the signalling cell and only influence cells that contact it
-need to be close to each other
-some cell extend long and thin processes to make contact
-contact results in conformational change in the target cell protein which activate signal transduction pathways

Question 5

What is an example of contact-dependent signalling

Answer 5

Notch signalling
-signal cell expresses delta
-target cell expresses notch
Notch translocates to the nucleus and acts as a transcription factor

Question 6

Outline paracrine signalling

Answer 6

Signalling cell secretes signal molecules-local mediators- locally into the extracellular fluid
Local mediators only act on cells in the near vicinity of the signalling cell

Question 7

Give an example of paracrine signalling

Answer 7

Hedgehog signalling

Question 8

Outline synaptic signalling

Answer 8

Action potential generated, stimulates release of neurotransmitters
-form of paracrine signalling
-local environment- synaptic cleft
-local mediators- neurotransmitters

Question 9

Outline endocrine signalling

Answer 9

Secrete signal molecules(hormones) into the bloodstream
Blood carries the hormones far and wide- can act on distant tissue and cells

Question 10

Give an example of endocrine signalling

Answer 10

Insulin- response to high glucose
Growth hormone-stimulates growth from pituitary gland

Question 11

Outline ion-channel-coupled receptor

Answer 11

Open in response to a specific stimulus
-binding of ligand
-change in voltage
-mechanical stress
Show ion selectivity
The ligand can be an extracellular mediator such as a neurotransmitter or intracellular mediator

Question 12

Outline G protein-coupled receptors

Answer 12

Large family of proteins
Seven transmembrane domains
G-protein-coupled receptors act by indirectly regulating the activity of a separate plasma membrane-bound target protein
Mediated by G protein (trimeric GTP-binding protein)

Question 13

Outline cAMP

Answer 13

Synthesised from ATP by adenylyl cyclase
Continuously degraded by cyclic AMP phosphodiesterase
A second messenger protein