Cell Communication SEM1 Flashcards

1
Q

What are gap junctions

A

Cell-cell junctions between apposed plasma membranes - direct connect for small soluble signals (not large molecules)

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2
Q

What signals are moved across membranes through vesicle fusion (exocytosis)

A

-proteins
-peptides
-amino acids
-nucleotides

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3
Q

What signals are released through channels and transporters

A

Ions

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4
Q

What does it mean for a signal to be released constitutively

A

Passive flow down concentration gradient

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5
Q

What does it mean for a signal to be evoked when released

A

Channels can be gated

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6
Q

What signals are released through free diffusion

A

Steroids
Gasses
(Both are hydrophobic)

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7
Q

What are the three main forms of signaling of secreted molecules

A

-paracrine
-synaptic
-endocrine

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8
Q

What is the action of signals released through paracrine signaling

A

Released signals only affect cells in the immediate cellular environment

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9
Q

How do signals terminate in paracrine signalling

A

-uptake into neighboring cells
-destruction by extracellualr enzymes
-sequestration by extracellular matrix

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10
Q

What is the action of signals released through autocrine signalling

A

The signal is released onto the same cell type

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11
Q

What can a group of identical cells in autocrine signaling result in

A

Group of identical cells produces a higher concentration secreted signal than a single cell can - 1 cell releases signal, binds to receptors on neighboring cells => amplify signal

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12
Q

What does the activation of the dendrite trigger in synaptic signaling

A

-activation at dendrite triggers electrical impulses (action potentials) along neuronal axon

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13
Q

What happens when an impulse reaches the nerve terminal in synaptic signalling

A

It stimulates secretion of chemical neurotransmitters

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14
Q

What is the role of endocrine cells

A

Secrete signals - hormones - into the blood

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15
Q

How is specificity of signalling maintained in endocrine signalling

A

Only certain cells have appropriate receptors to recognise specific hormone

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16
Q

How can specificity of signalling be achieved by synaptic signalling

A

Arises from the physical location of the signalling site and the receptor

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17
Q

How can specificity of signalling be achieved by endocrine signalling

A

Arises from combination of different signalling molecules being recognised by equally array of receptors (wide range of signals and receptors)

18
Q

What is the difference in distance travelled by endocrine and synaptic signalling

A

-endocrine targets anywhere in body - long distance
-synaptic targets 100nm away from signal -short distance

19
Q

What is the difference in speed between endocrine and synaptic receptors

A

-endocrine realised on diffusion and blood flow to reach target - slow
-synaptic signals take <1 sec to reach target - fast

20
Q

What is the difference between the affinity of target between endocrine and synaptic signalling

A

—endocrine signals diluted in bloodstream - receptors high affinity
-synaptic signals highly concentrated at synapse - receptors low affinity

21
Q

Which cells do not require receptors

A

Cells that use signalling via gap junctions or gasses

22
Q

What does binding of the signal (ligand) cause

A

Receptor activation

23
Q

What does receptor activation stimulate production of

A

Stimulates production of intracellular signals

24
Q

Where are receptors located in relation to steroid signalling

A

Receptors located within the cell

25
Q

What are the 4 major types of receptors

A

-ionotropic
-metabotropic
-kinase
-steroid

26
Q

Function of ionotropic receptors

A

Allow flow of ions across membranes

27
Q

Function of metabotropic receptors

A

Generate new signals inside cell (2nd messengers)

28
Q

Function of kinase receptors

A

Modify existing molecules to generate new signals

29
Q

Function of steroid receptors

A

Change expression of genes

30
Q

What effect can ionotropic receptors induce

A

Changing the membrane potential

31
Q

What are the two types of ionotropic receptors

A

Excitatory - influx of positive charged ions e.g Na+ or Ca2+
Inhibitory - influx of negative charged ions e.g Cl-

32
Q

How do metabotropic or G-protein-linked receptors act to regulate the activity of a plasma-membrane-bound target protein

A

The receptors act indirectly to a target which is either an enzyme or an ion channel

33
Q

What is the intermediate between the receptor and target in metabotropic processes

A

A trimeric G-protein

34
Q

What are the 3 subunits of G-proteins

A

Alpha (a), beta (B) and gamma (y) subunits

35
Q

What do the subunits of g-proteins bind to

A

Bind to metabotropic receptors which have 7 transmembrane domain structures (Metabotropic and G protein linked receptors have same structures)

36
Q

How is the G-protein attached to the receptor and membrane

A

Attached to receptor by its alpha (a)- subunit
Attached to membrane by its alpha(a) and gamma(y)-subunits

37
Q

What does the ligand binding cause the alpha(a subunit to release

A

Releases GDP for GTP (gtp replaces gdp and binds to alpha subunit of protein)

38
Q

What does ligand biding and the a-subunit release of GDP and GTP cause

A

1)activation of the alpha(a) subunit and
2)release of the beta(B)/gamma(y) subunits

39
Q

What does the activation of the alpha-subunit allow for

A

To alter enzyme activities therefor change concentration of intracellular signals inside cell

40
Q

How is signalling from metabotropic receptors terminated

A

Terminated by hydrolysis of GTP to GDP by the alpha-subunit

41
Q

What are kinase receptors

A

Either enzymes themselves or associated with enzymes

42
Q

What is the structure of a kinase receptor

A

One transmembrane domain with a ligand binding site outside the cell and enzyme activity inside cell