Cell signalling Flashcards

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1
Q

Outline main stages of ligand receptor interxn

A
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2
Q

Outline signal transduction (phosphorylation cascade and signal amplification)

A

Signal transduction is a multi step cascaded pathway, amplifies signal by 1) Phosphorylation/dephosphorylation 2) 2nd messenger

Each step more PDT than preceding step

Phosphorylation cascade: Seq. of phosphorylation rxns relay proteins phosphorylates subsequent protein kinases

Phosphotases remove phosphate grps from proteins, inactivating protein kinases

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3
Q

Describe ion channel receptor

A

Transmembrane protein subunit
1) extracellular ligand
2) gated hydrophilic channel

  1. Ligand binds to receptor, conformational change, channel.opens
  2. Ion flows in changing conc.
  3. Ligand dissociates, gate closes
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4
Q

Outline cellular response

A

Cells respond by
1) regulating protein/enzyme activity
2) transcription of genes

Same signal -> can have diff response
Same receptor -> diff relay proteins

Same cell w diff receptors can receive diff signals
Efficiency of signal transduction increased by scaffold proteins (activate phosphorylation cascade)

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5
Q

Role + nature of 2nd messenger (eg. cAMP)

A

Small non protein moleq/ions
Water soluble cAMP Ca2+
Lipid soluble DAG
Short-lived

ROLE:
Relay info from complex to other proteins
Bind and alter conformation of other proteins
eg. G protein activates adenyl cyclase
Which then catalyses ATP to cAMP

cAMP then activates PKA
-> Phosphorylates other proteins (transcription of genes)

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6
Q

Betas -> need insulin
Outline how insulin regulates blood glucose concentration. (TKR)

A

When blood glucose conc. above 90mg
Beta cells of ioL of pancreas release insulin

1) 2 insulin moleq bind to complementary 2 insulin receptor CSM -> LIVER & MUSCLES
- Conformational change, dimerise

2) activated dimer transmits signal to catalytic TK tail

3) TK cross phosphorylates multiple tyrosine residues
Activates insulin receptor substrate

4) IRS triggers variety of relay proteins -> responses

Increase of
- transport of GLUT glucose tpts
- glycogenesis
- glycolysis
- FAT synthesis

Decrease of
- glycogenolysis (hydrolysis of glycogen)
- gluconeogenesis (conversion to glucose)

Decrease blood glucose conc.

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7
Q

Alphas -> Glucagon
Outline how glucagon regulates blood glucose concentration (GPLR)

A

When glucose below 90mg
Glucagon released by alpha cells in ioL ONLY LIVER

  1. Glucagon binds to complementary GPLR activates receptor -> a. GPLR binds to inactive G protein
  2. G protein REPLACES GDP w GTP (activating it)
    Diffuse across CSM -> binds to adenyl cyclase
  3. Activated adenyl cyclase catalyses formation of cAMP from ATP
  4. High cAMP conc. activates PKA
  5. PKA phosphorylates & activates proteins

Increase
1) gluconeogenesis
2) glycogenolysis

Decrease
1) glycolysis
2) glycogenesis

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8
Q

Describe GPLR

A
  • 7 alpha helices spanning membrane (transmembrane)
  • Specific loops from binding sites for ligand & G protein

G protein
GDP -> inactive
GTP -> active

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9
Q

Describe TKR

A

Single alpha helix consisting
1. Extracellular ligand binding site
2. intracellular catalytic tail -> tyrosine kinase + tyrosine residues (Tyr is an am acid)

TK tail -> kinase enzyme catalysing phosphate grp from ATP

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10
Q

Advantages of cell signalling process

A
  1. Signal amplification -> small amt of signal produce large amt of pdts
  2. REGULATED
    allows for fine tuning, each step controlled independently
  3. SPECIFICITY
    Ligand specific to certain receptors on certain cell types
  4. Single signal molecule -> triggers multiple cellular rxns
    + Simultaneously diff cell types
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11
Q

Advantages of cell signalling process

A
  1. Signal amplification -> small amt of signal produce large amt of pdts
  2. REGULATED
    allows for fine tuning, each step controlled independently
  3. SPECIFICITY
    Ligand specific to certain receptors on certain cell types
  4. Single signal molecule -> triggers multiple cellular rxns
    + Simultaneously diff cell types
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