Week 9/10: Cell communication Flashcards

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1
Q

what is signal transduction

A

conversion of a signal from one physical or chemical form to another

e.g a signal molecule binds to a receptor and ends with a response

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2
Q

what is the general flow of information during cell signaling

A
  1. receptor-ligand binding
  2. Signal transduction (via the second messenger)
  3. Cellular response
  4. Change in gene expression (mitochondria)
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3
Q

how are extracellular signaling molecules released

A

by exocytosis or diffusion

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4
Q

what is a receptor

A

a specific protein capable of binding to the signal molecule

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5
Q

Are receptors transmembrane

A

most are

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6
Q

what begins the intracellular signalling pathway

A

activation of a receptor

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7
Q

what do intracellular signalling proteins do?

A
  • distribute the signal to different parts of the cell

- form different signalling pathways

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8
Q

what does a target protein do?

A
  • effector

- causes the cellular response or changes the cell behavior

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9
Q

What are the types of cell signaling

A

chemical: endocrine, paracrine
electrical: nervous, cell-cell contact

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10
Q

what is endocrine signaling

A
  • signal molecules are hormones
  • secreted by endocrine cells
  • carried through the bloodstream to act on target cells at distant body sites
  • bind receptors on target cells
  • long-distance communication = slow
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11
Q

what is an example of endocrine hormones

A

cortisol, adrenaline

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12
Q

what is paracrine signalling

A
  • signal molecules are local mediators
  • secreted by neighbouring cells
  • diffuse through extracellular fluid
  • short distance (fast)
  • autocrine: responds to signalling molecules produced themselves
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13
Q

Example of paracrine local mediators

A

nitric oxide, histamine, growth factors

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14
Q

neuronal signalling

A
  • long distance
  • quick and specific
  • Electrical impulses travel down an axon & are converted to a chemical signal (neurotransmitter) which acts on the target cell
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15
Q

Direct cell-cell contact

A
  • no molecule released
  • direct contact
  • fast
    eg. embryonic development
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16
Q

gap junctions

A

are protein channels made up of connexin

  • direct flow of signal to neighbouring cell: electrical ions, signal chemicals (eg. cAMP)
17
Q

CAMs

A

need direct surface contact

18
Q

what are the types of extracellular signal molecules

A
  • large hydrophobic molecules

- small hydrophobic molecules

19
Q

large hydrophobic molecules

A

Rely on cell-surface receptors to relay their message across the membrane

e.g. adrenaline, insulin, glucagon, adenosine, opiates, histamine, TGF-β

20
Q

Small hydrophobic molecules

A

Pass through the lipid bilayer

Once inside cell activate intracellular enzymes or bind to intracellular receptors
e.g. steroid hormones, nitric oxide

21
Q

Steroid Hormones

A

Nuclear receptor can be in cytosol or nucleus

Once activated it alters transcription in nucleus

Some hormone receptors are bound to DNA already

22
Q

molecular switches

A

Activation is achieved by either phosphorylation or GTP binding = molecular switches

23
Q

phosphorylation molecular switch

A

is a key way of activating or inactivating a protein

24
Q

protein kinase

A

enzyme that adds phosphate groups to proteins

25
Q

protein phosphatase

A

enzyme that removes phosphate

26
Q

GTP - binding molecular switch

A

Switch between active & inactive depends on binding of GTP or GDP

Intrinsic GTPase activity – shut
themselves down by GTP
hydrolysis

e.g. G proteins

27
Q

what are the 3 cell surface receptors

A
  1. ion-channel coupled
  2. G-protein coupled
  3. enzyme - coupled
28
Q

ion channel coupled receptors

A

nervous system
Convert chemical signals into electrical signals

Binding of a neurotransmitter alters the shape of the receptor allowing it to open or close

Ions specific to the channel move in or out of the cell based on their electrochemical gradient
e.g. Na+, K+, Ca2+ or Cl-

29
Q

G-protein coupled receptors

A

Many hundreds of GPCRs known in humans

Diverse family of receptors

Many of the drugs we use today act at these receptors

All GPCRs possess a similar structure
- Seven-membrane spanning protein domains

30
Q

cholera

A

Toxin continually activates G protein and adenylate cyclase in the gut cells resulting in abnormally high amounts of cAMP

Causes unregulated secretion of electrolytes (Cl, Na+, K+, bicarbonate) & massive outflow of water (“rice water” stools)

31
Q

Rapid signalling

A

cyclic amp response

32
Q

slow signalling

A

involves gene regulation

33
Q

Enzyme coupled receptors

A

respond to signals that regulate cell growth, proliferation, differentiation & survival, as well as rapid reconfigurations of cytoskeleton etc.

34
Q

what are enzyme coupled receptors

A

transmembrane proteins

35
Q

what is the largest class of enzyme coupled receptors

A

receptor tyrosine kinase