S1) Biological Signalling Molecules

Question 1

What is pharmacology?

Answer 1

Pharmacology is the study of molecular signallers regulating physiological processes

Question 2

What are the main extracellular signalling groups?

Answer 2

• Autocrine
• Paracrine
• Endocrine

Question 3

Classify the 3 main extracellular signalling groups by the distance / volume over which they act

Answer 3

• Autocrine: target site is on the same cell (self stimulation)
• Paracrine: target site is on adjacent cell
• Endocrine: target site is on distant cell (travels through blood)

Question 4

Describe 2 properties of endocrine signalling molecules

Answer 4

• Highly potent
• Global signal route (released into bloodstream)

Question 5

Identify the 3 major types of endocrine signalling molecules

Answer 5

- Hydrophilic 1: amino acid derivatives

- Hydrophilic 2: peptides

- Lipophilic: steroids

Question 6

Describe 3 properties of amino acid derivatives (hydrophilic 1 molecules)

Answer 6

• Small
• Hydrophilic (charged)
• Plasma membrane receptors (extracellular)

Question 7

Describe 2 properties of peptides (hydrophilic 2 molecules)

Answer 7

• Chain length varies
• Plasma membrane receptors (extracellular)

Question 8

Describe 2 properties of steroids (lipophilic molecules)

Answer 8

• Derived from cholesterol
• Nuclear receptors (intracellular)

Question 9

Identify 3 examples of endocrine signalling molecules

Answer 9

• Adrenaline (A&E use)
• Insulin (diabetics)
• Steroids (anti-inflammatories)

Question 10

State 3 actions of paracrine signalling molecules

Answer 10

• Signalling coupled from cell-to-cell
• Molecules are released into extracellular environment
• Induces changes in receptor cells (behaviour/differentiation)

Question 11

Neurotransmitters are example of a paracrine signalling molecule.

Describe their mechanism of action

Answer 11

Neurotransmitters allow for the tight coupling of signalling molecule transmission over synapse (electrochemical)

Question 12

Distinguish between the actions of the excitatory and inhibitory neurotransmitters

Answer 12

• Excitatory: signal increase firing rate post synaptically
• Inhibitory: signal decrease firing rate post synaptically

Question 13

Identify the 3 different neurotransmitters

Answer 13

• Acetylcholine
• Monoamines
• Amino acids

Question 14

Provide 3 examples of amino acid neurotransmitters and their signalling function

Answer 14

- Glutamate: excitatory

- Glycine: inhibitory

- Gaba: inhibitory

Question 15

Provide 3 examples of monoamine neurotransmitters and their signalling function

Answer 15

• Adrenaline: excitatory

- Noradrenaline: excitatory

- Dopamine: excitatory & inhibitory

- Serotonin: excitatory

Question 16

What is the signalling function of acetylcholine?

Answer 16

Excitatory at an end organ

Question 17

Provide 3 examples of paracrine signalling molecules in use

Answer 17

• Parkinsonism: uses dopamine precursors
• Epilepsy: uses GABA receptor modulators
• Hypertension: antagonises adrenaline/noradrenaline

Question 18

What is the action of autocrine signalling molecules?

Answer 18

Cells respond to their own released signalling molecules

Question 19

What happens when signalling molecules bind to their target?

Answer 19

• Signalling molecules bring about a change in functional status
• Original signal is transformed to produce another signal which performs a signal-dependent specific task

Question 20

How can drug targets be classified?

Answer 20

R – receptor

I – ion channels

T – transporters

E – enzymes

Question 21

How can receptors be classified?

Answer 21

• Kinase linked Receptors
• Ligand gated/Ionotropic Receptors
• Nuclear Receptors (intracellular)
• GPCRs (metabotropic)

Question 22

Describe the action of Kinase linked Receptors

Answer 22

• Mediate signals of wide variety of protein molecules
• E.g. growth factors cytokines hormones*
• Act via phosphorylation of specific groups
• E.g. Growth/differentiation*

Question 23

Describe the action of Ionotropic receptors

Answer 23

• Bind with ligand gate ion current for duration of binding
• Allow ion currents and voltage change
• E.g. fast neurotransmitters* ACh & GABA

Question 24

Describe the action of nuclear/intracellular receptors

Answer 24

• Ligands need to be lipid soluble e.g. steroids
• Bound ligand-receptor complex migrates to nucleus (if not already there) then binds to gene transcription factor
• Activates/inactivates a gene or set of genes

Question 25

Describe the action of G-Protein Coupled Receptors

Answer 25

• Largest receptor group
• Slow neurotransmitters e.g. Musc ACh, serotonin, adenoreceptors
• Three major types: G_s, G_i, G_q

Question 26

What are the functions of ion channels?

Answer 26

• Selectively allow ion current to flow across the plasma membrane
• Regulate voltage signals in excitable cells maintain membrane potential

Question 27

What are the four major ion currents?

Answer 27

Question 28

What is the function of transports/carriers?

Answer 28

Transport of ions / small molecules that can use channels (facilitated diffusion)

Question 29

When is transport needed and what does it use?

Answer 29

• Transport needed if highly polar or going against gradient e.g. Na⁺/K⁺ ATPase
• Uses ATP as energy source or pre-existing ion gradient (symport/antiport)

Question 30

What are enzyme functions?

Answer 30

Signal Processing Transformation:

• Synthesis
• Degradation

Question 31

How can one target enzymes?

Answer 31

• Competitive inhibition at active site
• Increase levels of precursor substrate