Signalling

Question 1

What are the 3 ways cells communicate with one another?

Answer 1

1) Remote signalling by secreted molecules
2) Contact signalling by plasma membrane-bound molecules (juxtacrine signalling)
3) Contact signalling by gap junctions

Question 2

Name the 4 types of cellular signalling and each secretion.

Answer 2

Autocrine - repsonds to signals from self secreted molecules
Paracrine - secreted by itself to act on nearby cells
Endocrine - travels in blood to act on distant target cells
Neuronal - responds to nerve impulse by releasing neurotransmitter to act on nearby cells

Question 3

Name 2 categories of hydrophilic hormones.

Answer 3

1) Catecholamines - adrenaline, noradrenaline, dopamine

2) Peptide hormones - gastrin, insulin, gulcagon

Question 4

Name 3 categories of lipid-based hormones.

Answer 4

1) Steroids - oestrogen, testosterone, cortisol
2) Thyroid hormones - T3, T4
3) Sterol hormones - calcitrol

Question 5

Where do receptors of hydrophilic hormones live in a cell?

Answer 5

On cell membrane

Question 6

Where do receptors of lipid-based hormones live in a cell?

Answer 6

Inside cell

Question 7

Name 4 types of receptors.

Answer 7

cell-surface:
1) Ligand-gated ion channels
2) Gprotein-coupled-receptors (GPCRs)
3) Kinase-linked receptors
intracellular:
4) Nuclear receptors

Question 8

What is the speed of ligand-gated ion channels?

Give an example of one.

Answer 8

Very fast binding and channel opening –> fast synaptic transmission
GABA

Question 9

What do GPCRs target?

Give examples of some.

Answer 9

Neurotransmitters
Peptide hormones
egs: ACh receptor, angiotensin II receptor

Question 10

Give an example of a catalytic kinase-linked receptor.

What does this mean?

Answer 10

Insulin

The receptor itself is an enzyme

Question 11

Give an example of a non-catalytic kinase-linked receptor.

What does this mean?

Answer 11

Cytokine

The receptor acts through cytoplasmic tyrosine kinases

Question 12

What 3 processes do kinase-linked receptors control?

Answer 12

1) Apoptosis
2) Cell division
3) Tissue repair

Question 13

What happens with nuclear receptors?

Answer 13

Regulate gene transcription:
hormones diffuse across plasma membrane and interact with cytosolic/nuclear receptors to form hormone-receptor complexes –> bind tor regions of DNA –> affect gene transcription

Question 14

What are the roles of the 4 parts of a nerve?

Answer 14

Nerve cells (neurons) = electrically excitable
Dendrites = receive information
Cell body = assimilates info
Axon = ends at nerve terminal

Question 15

Put the life cycle of a neurotransmitter in order:
Storage
Receptor activation
Synthesis
Release
Neurotransmitter inactivation

Answer 15

1) Synthesis
2) Storage
3) Release
4) Receptor activation
5) Neurotransmitter inactivation

Question 16

What are the 2 different types of depression?

Answer 16

1) Unipolar depression

2) Bipolar affective disorder

Question 17

Treatments for depression

Answer 17

Monoamine reuptake inhibitors
Monoamine oxidase inhibitors
Miscellaneous atypical antidepressants
Electroconvulsive therapy (ECT)
Mood-stabilising drugs

Question 18

What type of signalling is responsible for enzymatic production of NO, CO and H2S?

Answer 18

Paracrine

Question 19

Name 2 protective qualities of CO.

Answer 19

Cardioprotective

Neuroprotective

Question 20

What are the 3 main stages to signal transduction?

Answer 20

1) Reception
2) Trnasduction
3) Response

Question 21

From top to bottom describe the 4 elements to the signal transduction hierarchy.

Answer 21

1) Cell
2) 1st messenger
3) Receptor
4) Response

Question 22

In the full hierarchy where are the 3 main sites of amplification?

Answer 22

G proteins
Effector enzymes
Protein kinases

Question 23

What is the role of G proteins?

Answer 23

GTPases hydrolysing GTP –> GDP

Question 24

What are the 2 major groups of G proteins?

Give exmaples of each.

Answer 24

G proteins
eg: Ga, Gs, Gq
Small GTPases
eg: Ras Rho

Question 25

What happens when a ligand binds to a ligand binding site?

Answer 25

G protein releases GDP and swaps it for GTP --> G protein activated

Question 26

What happens to the GTP bound alpha, beta, gamma molecule when a G protein binds?

Answer 26

GTP bound alpha dissociates from the beta and gamma subunits

Question 27

Gs: What is its effect? What is its effector enzyme? What happens to its 2nd messenger?

Answer 27

Stimulation Adenylate cyclase cAMP increases

Question 28

Gi What is its effect? What is its effector enzyme? What happens to its 2nd messenger?

Answer 28

Inhibition Adenylate cyclase cAMP decreases

Question 29

Gq What is its effect? What is its effector enzyme? What happens to its 2nd messenger?

Answer 29

Stimulation Phospholipase C DAG and IP3 increase

Question 30

Name a toxin which acts as a Gs protein. What disease results? How does it work?

Answer 30

Cholera toxin Cholera Prevents GTPase activity of Gs --> Gs remains activated --> overstimulation of adenylate cyclase --> accumulation of cAMP --> increased loss of Cl- --> osmotic movement of water into gut lumen --> diarrhoea

Question 31

Name a toxin which acts as a Gi protein. What disease results? How does it work?

Answer 31

Pertussis toxin Whooping cough Prevents GTP/GDP exchange --> Gi remains inactivated --> cannot inhibit adenylate cyclase --> accumulation of cAMP --> increased insulin secretion/sensitivity to histamine

Question 32

What enzyme is responsible for: | GTP --> cyclic GMP + PPi

Answer 32

Guanylate cyclase

Question 33

In Gq activation what is released as a result of IP3 releasing into cytosol?

Answer 33

Calcium

Question 34

Which protein kinase is activated by DAG?

Answer 34

Protein kinase C

Question 35

Describe the pathway if an adrenaline ligand bound to a Gs protein.

Answer 35

``` Protein kinase A: Adrenaline binds to B1-AR --> Gs activated --> adenylate cyclase stimulated --> increased cAMP ```

Question 36

Describe the pathway if an acetylcholine ligand bound to a Gi protein.

Answer 36

``` Protein kinase A: Acetylcholine binds to Muscarinic M2 receptor --> Gi activated --> adenylate cyclase inhibited --> decreased cAMP ```

Question 37

Describe the pathway if an angiotensin II ligand bound to a Gq protein.

Answer 37

``` Protein kinase C: Angiotensin II binds to AT1R --> Gq activated --> phospholipase C stimulated --> increase in DAG/IP3 IP3 --> calcium: --> protein kinase C or --> Ca/CaM kinase ```

Question 38

Describe the pathway of protein kinase G if a neuropeptide/NO ligand bound.

Answer 38

Protein kinase G: Neuropeptide/NO binds --> guanylate cyclase stimulated --> increased cGMP