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Flashcards in ICPP Deck (163)
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1

What is the difference between exogenous and endogenous signalling molecules?

Exogenous = from outside the body

Endogenous = made within the body

2

Outline the main features of AMINE signalling molecules
(Solubility, Plasma 1/2 life, Time of action, Receptor location, mechanism)

Hydrophillic
Plasma half life = seconds
Time of action = milliseconds to seconds
Receptors in the plasma membrane
Mechanism = changes membrane potential + triggers synthesis of cytosolic 2nd messengers

3

Outline the main features of PEPTIDE and PROTEIN signalling molecules
(Solubility, Plasma 1/2 life, Time of action, Receptor location, mechanism

Hydrophillic
Plasma half life = minutes
Time of action = minutes to hours
Receptors located on the plasma membrane
Mechanism - triggers protein kinase activity + the synthesis of cytosolic 2nd messengers

4

Outline the main features of STEROID signalling molecules
(Solubility, Plasma 1/2 life, Time of action, Receptor location, mechanism

Lipophillic
Plasma half life = hours
Time of action = hours to days
Receptors in they cytoplasm or nucleus
Mechanism is the receptor-hormone complex controls transcription and mRNA stability

5

What are the three main types of signalling molecules used in the endocrine system?

Amines
Peptides (+proteins)
Steroids

6

What are some examples of local chemical mediators?

Cytokines (eg. Interleukins, chemokines, interferons, histamine)
Eicosanoids (eg. prostaglandins + leukotrines)
Neuropeptides

7

What type of signalling molecules does paracrine signalling use?

Neurotransmitters (amino acids, mono amines, peptides + ACh)
Local chemical mediators (cytokines + eicosanoids)

8

What are the types of signalling molecule targets?

Receptors
Ion channels
Transporters
Enzymes

9

What are the main types of receptor?

Kinase linked
Ion channels (ligand gated) - ionotropic
Nuclear (intracellular)
GPCRs - metabatropic

10

By what mechanism do kinase linked receptors work?

Phosphorylation of groups to start a signalling cascade

11

What neurotransmitters are taken up using cotransport of Na+?

Noradrenaline
Serotonin
Glutamate

12

What is an agonist?

Signalling molecule which binds to a receptor and activates it - causes a measurable response

13

What is an antagonist?

Signalling molecule that binds to a receptor but doesn't activate it - blocks the actions of agonists

14

Outline the main features of GPCR structure

Single polypeptide chain
7 Transmembrane domains
N terminal is extracellular
C terminal is intracellular

15

What is a G protein?

Guanine nucleotide binding protein
Heterotrimeric - has alpha, beta and gamma subunits

16

How are G proteins activated?

Replacement of GDP with GTP

17

What happens when GTP binds to the alpha subunit of a G protein?

The beta/gamma subunit dissociates and now both can go on to interact with effector proteins

18

When does the activity of G protein subunits stop?

When GTP on the alpha subunit is hydrolysed back to GDP (carried out by GTPase)
Alpha subunit has a high affinity for the beta/gamma subunit so the G protein is easily reformed

19

What ligands bind to Beta-adrenoreceptors?

What is their effect?

What is the effector molecule?

Adrenaline and noradrenaline

Stimulatory

Adenylyl cyclase

20

What are the types of alpha-adrenoreceptors?
Give their effect and what their effector molecules are.

Alpha 1 = Stimulatory - phospholipase C
Alpha 2 = Inhibitory - adenylyl cyclase

21

What GPCRs does ACh act on?
What is its effect on these? Give the effectors the G proteins act on

M1+M3 muscarinic receptors - Stimulatory (Gq protein) - acts on phospholipase C

M2+M4 muscarinic receptors - inhibitory (Gi protein) - acts on adenylyl cyclase

22

How does Cholera toxin (CTx) interfere with G protein function?

Prevents termination of signalling - stops Gs proteins hydrolysing GTP to GDP by systematic modification
G proteins continue to activate adenylyl cyclase to activate cAMP

23

How does Pertussis toxin (PTx) interfere with G protein function?

Covalently modifies GPCRs what prefer Gi proteins so they can no longer be stimulated - uncoupling

24

What does phospholipase C do to PIP2?

Convert it to IP3 and DAG

25

What is needed to convert PIP2 to PIP3?

PI3K

26

How many subunits does PKA have and what do they do?

4 Subunits

2 R - regulatory, binding of cAMP to these causes them to release the C subunits
2 C - catalytic, carry out phosphorylation of target proteins

27

What concentration is cytoplasmic Ca2+?

1 x10-7M (100nM)

28

What concentration is extracellular Ca2+?

1 x10-3M (1mM)

29

How is cytoplasmic Ca2+ increased?

VOCCs (voltage gated calcium channels)
LGICs (ligand gated ion channels)
CICR (Calcium induced calcium release)

30

How is cytoplasmic Ca2+ decreased?

PMCA (plasma membrane Ca2+ ATPase)
NCX (Na+/Ca2+ exchanger)
SERCA (Smooth/sarco endoplasmic reticulum ATPase)