7: Cell Communication 1

Question 1

What allows communication between cells?

Answer 1

Gap junctions

Question 2

What are gap junctions made up of?

Answer 2

Connexin proteins

• Gated by Ca2+, voltage and membrane potential, also phosphorylation
• Referred to as ‘electrical synapses’

Question 3

What are the two main classes of receptor and messenger/ligand?

Answer 3

• Water soluble chemical messengers

- Lipid-soluble chemical messengers

Question 4

How does water-soluble chemical messengers work?

Answer 4

signals can’t diffuse through the plasma membrane, so they bind to plasma membrane receptors. Activate specific cellular signalling

Question 5

How do lipid-soluble chemical messengers work?

Answer 5

Diffuse through the plasma membrane and bind intracellular receptors located in the cytoplasm or nucleus. Alters transcription

Question 6

What are the 4 types of plasma membrane receptors

Answer 6

1. Ion channel linked receptors aka ionotropic receptors
2. G protein coupled receptors (GPCR) aka metabotropic
3. Enzyme linked receptors
4. Regulated intramembrane proteolysis

Question 7

Draw/label an ion channel linked/ionotropic receptor

Answer 7

–

Question 8

Draw/label a G protein coupled receptor/metabotropic receptor

Answer 8

–

Question 9

Draw/label an enzyme linked receptor

Answer 9

–

Question 10

What are some chemical messengers/signals for ion channel linked receptors

Answer 10

Neurotransmitters (acetylcholine, glycine, GABA, glutamate), purines, serotonin

Question 11

What are some signals for enzyme linked receptors

Answer 11

Nerve growth factor, growth hormone, insulin

Question 12

What are some signals for regulated membrane proteolysis

Answer 12

Amyloid precursor protien, Notch

Question 13

Describe the G protein signalling pathway (diagrams will help as well)

Answer 13

1. Ligands binds to receptor, which activates it
2. Receptor interacts with the G protein to promote a conformational change and the exchange of GDP for GTP
   GEFs facilitate the dissociation of GDP and the binding of GTP
3. G protein dissociates from the receptor
4. alpha GTP and beta-gamma subunits dissociate

(look though slides)

Question 14

What are the two ways that ion channels are able to be activated

Answer 14

Indirectly via GPCRs or

Directly by neurotransmitters

Question 15

Describe how ion channels can be activated indirectly via GPCR

Answer 15

1. Neurotransmitter binds
2. G protein is activated
3. G protein subunits or intracelular messengers modulate ion channels
4. Ion channel opens
5. Ions flow across membranes

(look through slides for full detail)

Question 16

Describe how ion channels are activated by neurotransmitters

Answer 16

1. Neurotransmitter binds
2. Channel opens
3. Ions flow across membrane

Question 17

Signalling through GPCRs -example 1: GPCRs coupled to Gαs, the effector adenylyl cyclase and cAMP

Answer 17

G protein complex
-Gαs

Effector
-Adenylyl cyclase

Second messenger
-cAMP

Cellular effect
-PKA phosphorylates target proteins

Question 18

Signalling through GPCRs: activation of kinase A (PKA)

Answer 18

G protein complex

Question 19

Switching off GPCR signal transduction pathways

Answer 19

slides