Brainscape's Knowledge GenomeTM

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


See full index

PHA112 > GPCRs 2 > Flashcards

GPCRs 2 Flashcards

1
Q

what is cAMP synthesised from?

A

ATP by plasma-membrane bound enzyme adenylyl cyclase

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

what is cAMP rapidly + continuously destroyed by?

A

phosphodiesterase (PDE) enzymes

hydrolyses cAMP to adenosine 5’ - monophosphate

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

what does the synthesis and degradation of cAMP involve?

A
  • loss of 2 phosphates
  • creation of cAMP
  • formation of 5’-AMP

irreversible steps

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

phosphodiesterase enzymes (PDE)

A

at least 10 subtypes

  • PDE 3, PDE 4 selective for camp
  • PDE 5 selective for cGMP

inactivated weakly by drugs

  • methylxanthines (caffeine)
  • rolipram (discontinued) PDE 4 selective
  • sildenafil (viagra) PDE 5 selective
  • milrinone (treats heart failure)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are PDE inhibitor used to treat?

A

cardiovascular + respiratory disease

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

what is the best example of the signal transduction role of cAMP?

A

beta-adrenoreceptor

stimulates G protein (GS) + activates AC

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

what does the beta adrenoreceptor do?

A
  • initiates breakdown of glycogen + inhibition of ist synthesis in liver + skeletal muscle
  • relaxation of smooth muscle e.g. bronchioles in treatment of asthma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

switch on process

A
  • adrenaline binds to beta-adrenoreceptor on cell -> adenylyl cyclase activates through Gs
  • cAMP formed in cell by alphaS subunit
  • exchanging GDPl for GTP
  • causes alphaS to dissociate from beta-gamma + activate adenylyl cyclase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

why is the lifetime of the active form of the alphaS short?

A

GTPase activity of alphaS = stimulated when alphaS binds to adenylyl cyclase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

switch off process

A
  • bound GTP hydrolyses to GDP
  • inactivating alphaS + adenylyl cyclase
  • alphaS reassociated with beta-gamma to reform inactive Gs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how does cAMP exert its effects in animal cells?

A

by activating enzyme protein kinase A (PKA)

changes cellular activity + generates response

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

what does PKA do?

A

catalyses transfer of terminal phosphate group of ATP to specific serine/threonine residues on certain proteins

  • inactive PKA consists of complex of 2 catalytic subunits + 2 regulatory subunits that bind cAMP
  • binding of cAMP alters conformation of regulatory subunits
  • causes them to dissociate from complex
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are the actions of PKA?

A

phosphorylates 2 other enzymes

  • first phosphorylase kinase which phosphorylates enzyme
  • = glycogen phosphorylase - activating release of glucose residues from glycogen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

stimulation of glycogen breakdown by cAMP in skeletal muscle

A
  • inactive A-kinase -> activate A-kinase (via add of cAMP)
  • inactive phosphorylase kinase -> active phosphorylase kinase via add of Phosphate
  • inactive glycogen phosphorylase -> active glycogen phosphorylase via add of Phosphate
  • glycogen -> glucose 1 phosphate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the second enzyme phosphorylated by PKA?

A

glycogen synthase

  • performs final step in glycogen synthesis from glucose
  • phosphorylation inhibits enzymes activity
  • stopping glycogen synthesis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what 4 groups of protein are able to dephosphorylate proteins phosphorylated by PKA?

A

phosphatases I, IIA, IIB, IIC

I plays imp role in response to cAMP
- counteracts phosphorylations brought about in adrenaline-stimulated muscle cells

17
Q

what is another target of PKA?

A

phosphatase inhibitor protein

  • when protein phosphorylated by PKA
  • binds to protein phosphatase I + inactivates it
18
Q

what can an increase in cAMP levels do?

A
  • stimulate glycogen breakdown
  • inhibit glycogen synthesis

thus maximising amount of glucose available to cell

19
Q

what enzymes catalyse the removal of phosphate groups from proteins making them inactive and available for reuse?

A

protein phosphatases

20
Q

what is the purpose of the cascade reactions?

A

amplification

to get a big response

21
Q

what are the actions of cAMP?

A

regulates many cellular processes

  • enzymes involved in energy metabolism
  • cell division + cell differentiation
  • ion transport
  • ion channels
  • contractile proteins in smooth muscle
22
Q

what does CREB stand for?

A

cyclic AMP response element binding protein

23
Q

what is CREB?

A
  • transcription factor activated by neuronal activity
  • key regulator of pathway producing changes in synaptic connections (moves to nucleus + activates creb)
  • forms new memories
  • inhibitors of PDE4 enhance memory
24
Q

muscarinic M2 receptor in heart?

A
  • ACh causes dec in broth force + rate of heart beating
  • couple to Gi protein
  • causes dec prod of cAMP (alphai) (inhibits ad cyc) -> dec in contraction force
  • opens K+ channels (beta-gamma subunit)
  • causes hyperopolarisation of SA node cells (becomes neg)
  • leads to dec in firing rate
  • dec in heart rate
25
Q

what are the actions of cAMP?

A
  • interacts directly with pacemaker current channels (iF)
  • activates PKA which phosphorylates calcium channels in cell membrane to inc open state
  • this inc plateau current - Ica
  • PKA phosphorylates phospholamban - regulatory protein associated with Ca2+-ATPase pump
  • inc affinity of pumps for Ca2+ -> removing Ca2+ faster + shortens systole
  • PKA phosphorylates delayed rectifier K+ channels -> inc depolarising iK
  • terminates plateau earlier -> shortens AP

SHORTENS EVERYTHING DOWN SO HEART CAN SPEED UP
opposite to beta gamma effect

26
Q

what does an inhibition of phosphate lead to?

A

inc in heart rate

27
Q

more calcium into cell means…

A

more forced contractions

28
Q

what does the autonomic nervous system modulate?

A

frequency of depolarisation of pacemaker

29
Q

sympathetic stimulation

A

NA binds to beta 1 receptors on SA nodal membranes

30
Q

parasympathetic stimulation

A

ACh binds to muscarinic receptors on nodal membranes

inc conductivity of K+ + dec conductivity of Ca2+

31
Q

cholera

A
  • caused by bacterium that secretes toxin Ctx
  • acts on alpha subunit of Gs
  • causes persistent activation of adenylyl cyclase
    (toxin inhibits G protein)
  • big amount cAMP produced
  • resulting in excessive secretion of fluid from GI epithelium
  • —> chronic diarrhoea
32
Q

pertussis toxin (Ptx)

A
  • secreted by bacterium causing whooping cough
  • acts on alpha subunit Gi
  • causes ADP - ribosylation of Gi
  • inactivates inhibitory G- protein
  • prevents deactivation of adenylyl cyclase
  • big amount cAMP produced
  • inc mucous secretion interference with many cellular functions

PHA112 (37 decks)

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