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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
Q

How is the binding to steroid hormones regulated

A
  • Laws of mass action
  • mass action equilibrium
26
Q

Explain how steroid molecules travel

A
  • 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
Q

Describe lipid messengers

A
  • always hydrophobic
28
Q

Describe gases molecules

A
  • hydrophilic
  • very small so can diffuse very quickly
29
Q

How do gas molecules signal

A
  • intracellular proteins ( NOT CELL SURFACE RECEPTORS)
30
Q

What is transmembrane signal transduction

A

a single binding case causing multiples 2nd messenger molecules/ions
- each protein kinase activate multiple downstream targets amplifying the effect

31
Q

What are the 4 major classes of signalling receptors

A
  • ion Channels
  • GPCRs
  • enzymatic
  • nuclear
32
Q

Describe ion channel receptors

A
  • liagns binds to ion channel opening it allwoing for the diffusion in iomns down a gradient
  • channel not always specfic
33
Q

Describe GPCRs ans how they work

A
  • 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
Q

Deescribe enzymaptic receptors

A
  • transmemebrane receptors
  • ligand binds directly to the receptors causing it to dimerise triggering enzyme activity
35
Q

Describe nucelar receptors

A
  • hydrophobic signals enetrting cells directly
  • binding to intracellular receptors producing ligand dependant transcription factors
  • post-translational modifications can occur
36
Q

What type of signalling occurs in a hair cell

A

juxtacrine
- 2 fates either hair cell of supporting tissue

37
Q

Explain lateral inhibition

A
  • 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
Q

What is notch signalling

A

signalling system that regulates
1. cell proliferation
2. cell fate
3. differentiation
4. apoptosis

39
Q

What is morphogenesis

A

the fate of cell through development during the embryonic phase

40
Q

What is a morphogen

A

locally signalling molcuels that diffuse and act over long distances to induce cellular respones and control growth and pattern throughout a tissue region

41
Q

How does a fruti fly progresses morphogenesis

A
  • 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
Q

What is the Turning Machine

A
  • now known as the computer
  • answered yes or no questions to ouput millions of possible outcomes
43
Q

How can a complex pattern form

A

2 morphogens interacting with each other
- 1 activator and 2 inhibitor
- both diffuse thorugh tissue creating an UNSTABLE SYSTEM creating unpredictable patterns

44
Q

What does unequal diffusion result in

A

destabilisng effects on systems

Biomedical Physiology (5 decks)

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