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Biomedical Physiology > Cell Signalling (W2) > Flashcards

Cell Signalling (W2) Flashcards

1
Q

Why do cells need to signal

A
  • location
  • growth
  • divison
  • motility
  • secretion
  • metabolism
  • death
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2
Q

How can chemical messengers alter protein structure

A
  • activating or deactivating exsisting enzymes
  • change gene expression
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3
Q

What are
- primary messengers
- secondary messengers

A
  1. bind to receptors to produce a direct response to the cell
  2. Secondary are produced in repose to a primary but not in its active from
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4
Q

What are the 4 indirect cell signalling pathways

A
  • autocrine
  • paracrine
  • endocrine
  • neuronal
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5
Q

What are the 2 direct cell signalling pathways

A
  • juxtacrine
  • gap juntion
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6
Q

Describe autocrine signalling

A

a ligand causes a response in the signalling cell itself

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7
Q

Describe paracrine signalling

A

a ligand causes a response in a neighbouring target cell by binding to a receptor

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8
Q

Describe endocrine signalling

A

a ligand is release via a gland travels through medium for a leg distance and reaches a target cell inducing a response

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9
Q

Describe nuclear signalling

A

via the nervous system - electrical impulses

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10
Q

Describe juxtacrine signalling

A

Communication that is cell-to-cell or cell-to-matrix requiring close contact

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11
Q

Describe gap junction signalling

A

communication through specialised protein functions bringing two cells together

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12
Q

What can cause gap junctions to close

A

increased calcium or decreased extracellular pH

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13
Q

Describe peptide messengers

A
  • always hydrophilic
  • packaged in vesicles via Golgi apparatus released by exocytosis
  • peptide signals are soluble in water and don’t require any transportation or carrier protein to circulate in aqueous solution
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14
Q

What happens if the peptide messenger membrane receptor is ;
1. ionotropic
2. metabotropic

A
  1. binding results in a change in the ion flux into the cell
  2. bindings causes a change in the enzyme activity in the cell
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15
Q

What stops the peptide hormones from continually signalling

A

protease/peptidase

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16
Q

Describe biogenic amine messengers

A
  • usually hydrophobic
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17
Q

What are catecholamines

A
  • derivative of tyrosine
  • all hydrophilic
  • e.g., dopamine, octopamine
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18
Q

What are indoleamines

A
  • derived form tryptophan
  • hydrophilic
  • e.g., serotonin , melatonin
19
Q

What are histamines

A
  • hydrophilic
  • amine metabolites of histidine
  • neurotransmitter + paracrine signalling molecule in all taxa
  • acts on different membrane receptors
20
Q

What is acetylcholine

A
  • hydrophilic
  • metabolite of choline
  • found in all taxa
  • acts via plasma membrane receptors
21
Q

What are thyroid hormones

A
  • hydrophobic
  • synthesised from tyrosine
  • only found in vertebrates
  • acts as hormones
22
Q

Describe steroid messengers

A
  • always hydrophobic
  • derivative form cholesterol
  • endocrine and paracrine hormones in all vertebrates and many invertebrates
23
Q

Where are the 5 classes of steroid hormones synthesised

A
  • mitochondria and SER
24
Q

Why can’t steroid hormones be stored within vesicles

A
  • they are lipophilic so are soluble in plasma membrane so must be synthesised immediately prior to their secretion

they will dissolve into the membrane as they hydrophobic

25
How is the binding to steroid hormones regulated
- Laws of mass action - mass action equilibrium
26
Explain how steroid molecules travel
- hormone molecules will bind to carrier proteins at the source where is a high concentration - in the circulatory system they will move quickly to where the unbound messenger concentration is much lower - results in unbinding of the messenger meaning the messenger can interact with the target cell
27
Describe lipid messengers
- always hydrophobic
28
Describe gases molecules
- hydrophilic - very small so can diffuse very quickly
29
How do gas molecules signal
- intracellular proteins ( NOT CELL SURFACE RECEPTORS)
30
What is transmembrane signal transduction
a single binding case causing multiples 2nd messenger molecules/ions - each protein kinase activate multiple downstream targets amplifying the effect
31
What are the 4 major classes of signalling receptors
- ion Channels - GPCRs - enzymatic - nuclear
32
Describe ion channel receptors
- liagns binds to ion channel opening it allwoing for the diffusion in iomns down a gradient - channel not always specfic
33
Describe GPCRs ans how they work
- ligands binds to N termius - binding causes a conformational change resulting in the release of GDP from alpha subunit - GDP to GTP - alpha dissociates from BY subunit to effector protein
34
Deescribe enzymaptic receptors
- transmemebrane receptors - ligand binds directly to the receptors causing it to dimerise triggering enzyme activity
35
Describe nucelar receptors
- hydrophobic signals enetrting cells directly - binding to intracellular receptors producing ligand dependant transcription factors - post-translational modifications can occur
36
What type of signalling occurs in a hair cell
juxtacrine - 2 fates either hair cell of supporting tissue
37
Explain lateral inhibition
- occurd between 2 cells - in 1 cells increased expression of delta cuases an increased expression of notch in the neighbouring cell - incresed notch cuases the cell decresaed delta and primary fate is inhbited - decreased delta in cell means increased notch in neigbouring cell causing primary fate to be adopted
38
What is notch signalling
signalling system that regulates 1. cell proliferation 2. cell fate 3. differentiation 4. apoptosis
39
What is morphogenesis
the fate of cell through development during the embryonic phase
40
What is a morphogen
locally signalling molcuels that diffuse and act over long distances to induce cellular respones and control growth and pattern throughout a tissue region
41
How does a fruti fly progresses morphogenesis
- Bicoid mRNA & nanos mRNA - Bicoid is tethered to the anterior - nanos is tethred to posterior - mRNA trnalsated to proteins produing a gradient by which bicoid or nanos diffuse to their ends
42
What is the Turning Machine
- now known as the computer - answered yes or no questions to ouput millions of possible outcomes
43
How can a complex pattern form
2 morphogens interacting with each other - 1 activator and 2 inhibitor - both diffuse thorugh tissue creating an UNSTABLE SYSTEM creating unpredictable patterns
44
What does unequal diffusion result in
destabilisng effects on systems

Biomedical Physiology (5 decks)

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