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Biology 2B03 > M6: Cell Signaling > Flashcards

M6: Cell Signaling Flashcards

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1
Q

Dictyostelium discoideum

A
  • eukaryote that transitions from a collection of unicellular amoebae into a multicellular slug and then into a fruiting body
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2
Q

two portions of a slug

A

prestalk (which forms the stalk portion of the fruiting body at the anterior end) and prespores (which forms the spore portion of the fruiting body at the posterior end)

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3
Q

What do dictyostelium eat?

A

feed on bacteria like E.coli

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4
Q

What happens to dictyostelium when food is abundant? What happens to it when food runs out?

A
  • when food is abundant, the single-cellular amoeba divides by mitosis
  • when food runs out, starved cells trigger production of cAMP which causes aggregation to occur
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5
Q

How does a single-celled amoeba turn into a multi-celled slug?

A
  • when food is low the amoeba aggregates which is triggered by cAMP which is produced by starved cells
  • the aggregated cells then form the slug
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6
Q

What happens to the slug once it is created?

A
  • it will differentiate to form the stalks and spores of the fruiting body
  • when food becomes available, the spores will germinate to form new amoebae
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7
Q

What is the signal for aggregation?

A

cAMP

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8
Q

What is the receptor for cAMP?

A
  • G-protein coupled receptor
  • the extracellular domain of GPCR binds to cAMP which activates the receptor
  • in response, cells move towards source of signal
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9
Q

What does signalling of cAMP initiate?

A

actin reorganization

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10
Q

What does a mutation in the gene for the clathrin heavy chain cause?

A

-unable to form vesicles for protein transport to cell membrane which results in no net movement towards source of signal

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11
Q

Neutrophils

A
  • white blood cells in our body that act similarly to Dictyostelium
  • they respond to bacteria and eventually neutrophils will capture and engulf the bacteria in process called endocytosis
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12
Q

What is the signal for produced by bacteria that causes neutrophils to follow it? What is the receptor?

A
  • signal: fMLP tripeptide produced by bacteria

- receptor: fMLP receptor (on surface of neurotophil); it is a G-protein coupled receptor

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13
Q

Signaling

A
  • transmission of information from one cell to another that induces a change in behaviour
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14
Q

Important concepts of signaling

A
  • production of signal
  • release of signal
  • perception of signal
  • interpretation of signal inside the target cell
  • resulting change in behaviour of the target cell
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15
Q

Step-by-step process of signalling

A
  1. Signaling cell produces and releases signalling molecule
  2. Target cell carries receptor that binds to that signal
  3. Binding activates receptor on target cell
  4. Activation initiates a cascade of chemical events inside target cell (STP) that interprets and transduces the signal
  5. Results in changes in target cell behaviour
  6. Signal must be removed to terminate target cell response.
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16
Q

What are two important factors that allow for surfaces of two molecules to bind? What are these factors responsible for?

A
  • Complementary shape -> allows surfaces of two molecules to come close together
  • Molecular complementary -> collection of non-covalent interactions that allow for/provide specificity and high affinity which allows for binding
17
Q

What occurs after binding of signal cell and receptor on target cell?

A
  • binding on extracellular domain of receptor on target cell causes conformational change in intracellular domain of receptor
  • this change induces the signal transduction pathway and then the cellular response
18
Q

Two levels at which specificity is achieved

A
  1. Specificity of ligand binding to receptor

2. Specificity of intracellular response mediated by STP

19
Q

Signal transduction pathways (STP)

A
  • collection of intracellular steps required to translate an extracellular signal into a cellular response
20
Q

Different types of signalling between cells

A
  • three main categories:
    1. Intercellular signaling (signalling between cells)
    2. Requires cell contact
    3. Target is on itself (acts alone)
21
Q

two types of intercellular signaling (i.e. signalling between cells without contact)

A

endocrine signalling and paracrine signalling

22
Q

Endocrine signalling

A
  • secreted signals released into circulatory system

- ex. hormones

23
Q

Paracrine signalling

A
  • secreted signals released into extracellular space to diffuse into neighbouring cells
  • ex. growth factors and neurotransmitters
24
Q

Proximal signalling

A
  • signalling cell and target cell are in direct contact with one another through cell adhesion mechanism
  • ex. sharing cytosolic messengers -> plasmodesmata (plants) and gap junctions (animals)
25
Q

Plasmodesmata

A
  • junctions between two neighbouring cells that span the cell membrane and the cell wall
  • connect the cytoplasm of neighbouring cells
  • found in plant cells
26
Q

Gap junctions

A
  • channels connecting the cytoplasm of neighbouring cells that allow for the fast diffusion of small molecules from one cell to another
  • found in animal cells
27
Q

Autocrine signalling

A
  • cells communicates with itself
  • signalling cell and target cell are the same
  • ex. growth factors produced to induce cell division or stop cell division
28
Q

How many classes of cell surface receptors are there?

A

seven

29
Q

Kd

A
  • concentration of ligand required to have half of maximal binding and represents receptor-signal affinity
  • ligand concentration where half receptors are occupied
30
Q

Much lower ligand concentration is required to achieve _________ than ligand concentration required to achieve ___________. What does this show?

A

1/2 maximal physiological response; fulling of 1/2 receptors

this show signal is amplified inside the cell and very little signal is required to exert a response

Biology 2B03 (6 decks)

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