Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PHA112 > GPCRs 3 > Flashcards

GPCRs 3 Flashcards

1
Q

to use Ca2+ as an intracellular signal, the resting cytosolic Ca2+ levels are kept…

A

low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the concentration of free Ca2+ in the cytosol?

A

less than or equal to 10^-7 M

extremely low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the concentration in the extracellular fluid + ER?

A

10^-3 M

high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what does the difference In concentrations allow?

A

a large gradient which drives Ca2+ into cytosol across plasma + ER membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

describe the events following a signal?

A
  • calcium channels open

- calcium ions enter cytosol triggering calcium responsive proteins in cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

for the signalling mechanism to work, what must the resting calcium ion concentration in the cytosol be kept?

A

low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how can you keep the calcium ion conc low?

A
  • keeping calcium ions out of cell

- keeping intracellular ca2+ low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

keeping calcium ions out of cell

A
  • cells have ca2+-ATPase in plasma membrane

- uses ATP to pump ca2+ out of cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

keeping intracellular ca2+ low

A
  • ca2+ pump in ER helps keep cytosolic [ca2+] low
  • if cell damaged, [ca2+] rises to high level (>10^-5 M) = dangerous
  • low affinity, high-capacity ca2+ pump in inner mitochondrial membrane takes up ca2+
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

give an example of a specific ca2+ binding protein?

A

calmodulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how many mechanisms are there altogether and how many are inside?

A

5 altogether

3 inside

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

ca2+ as an intracellular messenger

A

intracellular injection of ca2+ caused skeletal muscle to contract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

ca2+ entry into cells

A
  • depolarisation of PM -> influx of ca2+ via voltage-gated ca2+ channels
  • binding of mol to cell-surface receptors -> ca2+ release from ER
  • this = mediated via inositol trisphosphate (IP3)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what does the smooth muscle not need?

A

extracellular calcium to function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

when was the role of the membrane first described?

A

1953

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the most important inositol phospholipids?

A
  • PIP (phosphatidylinositol-phosphate)

- PIP2 - PI- bisphosphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

hydrolysis of PIP2

A

PIP2 breakdown begins with binding of signalling mol to G protein linked receptor

  • activated receptor stimulates trimeric G protein (Gq)
  • activates enzyme phospholipase c-beta
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is the best example of hydrolysis of PIP2?

A

m3 rat ileum receptor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

more than …. different cell-surface receptors use the hydrolysis of PIP2 pathway?

A

25

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

when PLC-beta cleaves PIP2

what 2 products does it generate?

A
  • IP3

- diacylglycerol (DAG)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

where does PLC cleave the bond?

A

cleaves between O of phosphate and CH2 of other mol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

IP3 diffuses through…

A

cytosol and releases Ca2+ from ER

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

DAG remains in the membrane and …

A

activates protein kinase C

24
Q

what are the 3 types of phospholipase C?

A

beta, gamma and delta

beta class activated by G protein linked receptors

25
Q

what is the journey of IP3?

A
  • leaves plasma membrane
  • releases ca2+ from ER by binding to IP3-gated ca2+ release channels in ER memb
  • channels regulated by POSITIVE feedback
  • released ca2+ binds back to channel to inc ca2+ release (CICR) - sensitive to ryanodine
26
Q

calcium + smooth muscle contraction

A
  • smooth muscle cells store ca2+ in ER and SR
  • released when IP3 receptor activated
  • IP3 generated by Gq linked receptor activation
27
Q

what is the contraction of smooth muscle activated by?

A

MLC phosphorylation

catalysed by myosin light chain kinases (MLCK)

activated when bound to ca2+ - calmodulin

28
Q

what do myosin phosphatase reverse?

A

phosphorylation + cause relaxation

29
Q

no regulatory proteins are involved in …

A

smooth muscle contraction

30
Q

function of ca2+ calmodulin complex

A
  • calmodulin binds to 4 ca2+ ions
  • calmodulin changes conformation, resulting in active complex
  • 2 globular hands of complex wrap around binding site on target protein
31
Q

role of ca2+ in cells

A
  • activate membrane ion channels
  • regulate enzyme activity
  • modulate protein function
  • regulate gene expression
  • kill cells! (necrotic + apoptotic death)
  • life and death messenger
32
Q

what is calcium the only link between?

A

electrical activity of neurone and end response of cell

33
Q

what triggers muscle contraction?

A

ca2+ liberation from SR

34
Q

what is different about the ca2+ unlike the other ions?

A

it is chemical signal carried that is important not the charge

35
Q

what are the sources of ca2+ to cells?

A
  • extracellular fluid (2mM)
  • plasma membrane channels
  • ligand gated channels (glutamate NMDA)
  • store operated channels (open when less ER calcium stores)
36
Q

what are the 2 mechanisms that operate to terminate the ca2+ response?

A
  • IP3 dephosphorylated by enzymes

- ca2+ that enters cytosol rapidly pumped out

37
Q

what happens to IP3 if it isn’t dephosphorylated?

A

phosphorylated to make IP4

38
Q

the enzyme that catalyses the production of IP4 is activated by…

A

increase in cytosolic (ca2+) induced by IP3

39
Q

why is the resynthesis of phospholipids important in regulation?

A

cell would run out of substrate

40
Q

at least how many reactions are involved in the metabolism of inositol lipids?

A

13

41
Q

the regulation reactions can be divided into 2 cycles

what are they?

A
  • inositol lipid cycle - occurs in membrane

- inositol phosphate cycle - occurs in cytosol

42
Q

what is PKC?

A

ca2+ dependent enzyme

43
Q

what does DAG increase the affinity of?

A

PKC for ca2+ -> activating enzyme

44
Q

what does activated PKC do?

A

phosphorylated specific target proteins that vary depending on cell type

45
Q

what are the several physiological functions of PKC?

A
  • secretion
  • modulation of ion conductance
  • control of growth + differentiation
46
Q

where are the highest concentrations of PKC found?

A

in brain

phosphorylates ion channels there

47
Q

G protein linked receptors can desensitise in 3 ways

what are they?

A
  • become altered so longer interact with G proteins (inactivation)
  • temp moved to interior of cell -> no longer have access to ligand (sequestration)
  • destroyed in lysosomes after internalisation (receptor down regulation)
48
Q

what does desensitisation depend on?

A

phosphorylation of receptor by PKA, PKC or G protein linked receptor kinases

49
Q

what do GRKs phosphorylate?

A

serine + threonines

50
Q

once receptor has been phosphorylated, what does it bind to?

A

member of arrestin family of proteins

51
Q

what can receptor desensitisation be classified into?

A
  • homologous

- heterologous

52
Q

what are the enzymes involved in receptor phosphorylation?

A
  • beta adrenergic receptor kinase (BARK)
  • cAMP- dependent protein kinase
  • protein kinase C (PKC)
53
Q

homologous desensitisation

A
  • BARK most imp

- capable of phosphorylating active agonist

54
Q

desensitisation of GPCR?

A
  1. inhibitory structural alteration of receptor
  2. receptor internalisation
  3. receptor degration

arrestin takes to Cathrin coated pits + degradation

55
Q

give examples of receptor up + down regulation?

A
  • cholesterol UP by statins
  • opiate UP by antagonist naloxone
  • beta adrenoreceptors UP by antagonist

PHA112 (37 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions