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1004 The Dynamic Cell > Cell Signalling And Pharmacology > Flashcards

Cell Signalling And Pharmacology Flashcards

1
Q

True or false?

PI3 kinase phosphorylates PIP2

A

True

PIP2 -> PIP3

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2
Q

True or false?

PI3 kinase phosphorylates and activates PKB

A

False… Why : PI3 doesn’t activate PKB. It facilitates the activation but doesn’t activate it DIRECTLY
>Only PKD1 does this

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3
Q

True or false?

PTEN phosphorylates PIP3 to shut down the Signalling pathway

A

False…PTEN is a phosphatase so REMOVES phosphate to form PIP2
It is a regulatory enzyme

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4
Q

True or false?

Molecules use pleckstrin homology (PH) domains to bind to PIP 3

A

True. PDK1 and PK-B has PH with PIP3 and then PDK1 activated PKB because of this closeness

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5
Q

Can calcium move through gap junctions?

A

Yes it can (waves of calcium… Perhaps the same as the ovum/embryo…….

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6
Q

True or false?

Calcium ions can indirectly exert its effects by binding to calmodulin

A

this is true

Calmodulin has 4 Ca2+ binding sites and undergoes conformational changes when bound.

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7
Q

Name stores of calcium

A

Sarcoplasmic recticulum, mitochondria and ER!

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8
Q

In paracrine signalling, the signalling molecule…

A

Acts on cells in close proximity to the secreting cell

So travels a short distance only

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9
Q

True or false?

In response to a signal, the cell can alter RNA transcription

A

This is true! Cell Signalling controls all biological events including RNA transcription

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10
Q

True or false?

Most signal receptors are found on the cell surface and bind to hydrophobic signalling molecules

A

False…. Why? First half is true but molecules are. HYDROPHILIC for extracellular signalling

Water soluble so can’t cross lipid bilayer

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11
Q

How do paracrine signalling molecules stay close to their point of origin?
give an example of such molecule

A

They have limited travel ability as they are easily degraded and inheritably unstable and quickly demobilised

e.g. Histidine or nitrous oxide

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12
Q

Cancer cells produce molecules to stimulate their own growth.
Which class of intercellular communication does this represent?
autocrine
paracrine
endocrine

A

Autrocrine signalling.

Cells have receptors for that molecule on themselves

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13
Q 
What type of signalling molecule is Ras?
A. Guanine exchange factor 
B. Protein kinase 
C. Protein phosphatase 
D. GTPase
E. None of these
A

Option D please.
All momomeric G proteins are GTPases!
It needs option A

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14
Q

Why do cell surface receptors use signal transduction pathways?

A

AMPLIFY the original signal and allows INTEGRATION of signals from other pathways
Allows more control and distribute the signal.
Faster communication within and between cell so faster responses.

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15
Q 
Which of these are not intracellular secondary messengers? 
A. cGMP
B. ATP
C. inositol triphosphate = IP3
D. Diacylglycerol = DAG
E. cAMP
A

Option B please.

ATP is not a signalling molecules. It is used to derive energy. Same with GTP!

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16
Q

True or false?

GEFs increase the GTPase activity of G protein

A

False… Why? They do GDP back to GTP so don’t degrade/hydrolysed the GTP
> GTP-ase activty = breaking down the GTP

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17
Q

In GPCR (gprotein coupled receptor) signalling, GTP binds to…
alpha
beta
gamma

A

The alpha subunit of trimeric G protein

Only the alpha subunit has GTPase activity

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18
Q

Ture or false

Cholera toxin modifies galpha S protein class

A 
This is. Ture!
It also prevents hydrolysis of GTP to GDP (so permeantly in active position) and overstimulates (effector molecule) adenylyl Cyclase activity = more cAMP
> Sclass for Stimulation
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19
Q

Which mechanisms can terminate intracellular signalling pathway

A

Degradation of extracellular ligand
Internalisation of activated receptor
Desensitisation of receptor
Deactivation of a signal transduction protein

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20
Q 
Which of these aren't commonly used in plant signalling?
A. Histidine kinase signalling 
B. Transcriptional repression of genes
C. Ca2+ signalling
D. GPCR signalling
E. Passive diffusion
A

Option D

Plants only have a handful of GPCR

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21
Q

True or false ?

Cryptochrome is a chromophore. Found in blue light receptors

A

This is true

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22
Q

True or false?

Phytochromes are intracellular receptors that detect light

A

True

23
Q

True or false?

Ethlyene receptor is deactivated by ethylene binding

A

True. Whe ethylene binds, the receptor is inactive, this stops the DEGRADATION of transcriptional regulator
So transcription of ethylene responsive gene can occur

24
Q

True or false?

Auxin receptors activate transcription factors to drive gene expression

A

This is false. Auxin receptors affects the repression proteins to remove it!
They don’t ‘t directly affect transcription factors

25
Q

What is a defining cell feature of dying cells in response to tissue damage (necrosis)

A

the cell swells

Also a reversible process

26
Q

cell features of Apoptosis

A

Cell shrinks
early changes are irreversible
Chromatin condense and fragments, small membrane bodies released and engulfed by other cells (apoptopic bodies)

27
Q

What is a feature of juxtacrine signalling?

A

It’s contact dependent as signalling cell is in direct contact with target cell.
Adjacent cells communicate with each other by gap junctions and connexin proteins

28
Q

describe ways in which calcium stores can increase or decrease

A

increase: influx of Ca through channel proteins from OUTSIDE cell or released from INTRACELLULAR stores
decrease: ATPase pumped back into stores or pumped out of the plasma mebrane // energy requiring as its AT!

29
Q

how does the alpha subunit of a trimeric G prtotein work?

A

dissociates from the beta and gamma subunits.

binds to an effector molecule which then amplifies or inhibts the signal

30
Q

how do Cytokine receptors differ from receptor tyrosine kinases?

A

they lack the intricnisc kinase activity so must RECRUIT soluble tyrosine kinase (janus kinase)

31
Q

give an example of electrical signalling in plants

A

venus fly trap: the sensory trigger hairs activate mechanosensitive ion channels which depolarises the memebrane= A.P
tugour pressure changes so leaflobes close and digest

32
Q 
Nuclear receptors are ligand activated transcription factors (directly activated by ligand). Which of these is a region that nuclear receptors do not have?
A Ligand binding domain
B DNA binding region 
C Hinge region
D catalytic region
E N terminal region
A

catalytic region!
>ligand and dna binding region recognise the ‘response elements’ of promoter region
> N terminal can be modified by other moelcules (phosphorlyation) to enhance trancription ability

33
Q

What dephosphorylates an active protein?

A

phosphatases

34
Q

Post Translational modification involves adding chemical functional groups to proteins. Name an example of this?

A

“Phosphorylation
Acetylation
Methylation
Hydroxylation”

35
Q 
Which of the following molecules are the second messenger for the G protein alpha i pathway and what effect has on its level:
A cAMP(increased)
B cGMP(increased)
C DAG(increased)
D cAMP(decreased)
E cGMP(decreased)
A 
OPTION D
cAMP decreased (as adenyly is inhibited)
> class i for inhibition!
36
Q

Drug action on receptors is dependent on many factors. What does this definition describe, “ A molecule that binds and activates a receptor, including signalling and a biological response
A agonist
B antagonist

A

agonist

37
Q

Adrenocorticotropic hormone (ACTH) travels through the bloodstream, enters connective tissue spaces, and attaches to specific sites on target-cell membranes. These recwptors are

A

transmemebrane receptors

38
Q

Ras structure and signalling is a monomeric G protein and is commonly activated by RTK’s. When is it active

A

when bound to GTP

39
Q

Phospholipase C is activated by which class of trimeric G protein?

A

G alpha q class

40
Q

How is cAMP produced ?

A

by the effector enzyme adenylyl cyclase which converts ATP to cAMP

41
Q

How would termination of the cell signal by removing the activated receptor from the cell membrane be achieved?

A

endocytosis

other ways of terminating signal cascade are to
>eliminate signalling molecule - Achesterase
> deactivate signal transduction proteins (e.g. PTEN)

42
Q

What moelcule phosphorylates an inactive protein to make it active?
What would it be if it were a lipid?

A 
protein kinase (exception glycogen synthase)
lipid kinase!
43
Q

Which molecule is used to dephosphorylate PIP3 to PIP2

A

PTEN - the phosphatase

44
Q

The most well studied receptors with intrinsic enzyme activity are the receptor tyrosine kinases (RTK’s). In order to activate RTK’s it:

A

Has a kinase that phosphorylates tyrosine’s on opposite receptor tail ie: transphosphorylation.

45
Q

if a cell loses its function of PTEN what can happen?

A

Cells lacking PTEN have elevated levels of PIP3 and PKB. Since PKB has ANTI-APOPTITIC effect, loss of PTEN indirectly reduces the programmed cell-death.
And PKB contributes to increased cell proliferation due to its involvement in cell division and growth

46
Q

Cancer cells commonly overexpress BCL2 which can result in
A increased apoptosis
B increased apoptosome formation
C decreased mitochondrial repiration
D Less effective chemotherapy treatment
E less PS flipping to inner leaflet of lipid bilayer

A

OPTION D

> there is LESS flippage as apoptosis ain’t happening BUT, it flips to the outerleaflet
more proliferation so MORE respiration is happening

47
Q

Which is false?
A apoptosis allows limb development
B APOPTOSIS provides counterbalance to cell division
C decreased apoptosis linked with degenerative disorder
D apoptosis triggered by defects in DNA

A

C is false statement!
INCREASED apoptosis linked with degenerative disorder
> as we lose too many cells

48
Q

which of the following statements about cholera toxin is false?
A modify the Galpha S protein class
B prevent the hydrolysis of bound .gtp to GDP
C lead to the continuous activation of adenyl cyclase
D modify the Galpha Q protein class.

A

OPTION D
> modifies the Galpah S subclass -> confromation of GTP permenatly active -> more cAMp -> salt and water loss -> cholera/ diahorrea/ dehydration

49
Q

in plant signalling, ubiquitin ligases
A can act as receptors for hormones
B direcly bind to dna to alter gene expression
C activated by red light
D activated by blue light
E directly bind and activate proteins by phosphorlyation

A

OPTION A

> auxin receptors are ubiquinated to target the protein (auxin hormone) for degredation

50
Q

which is true regarding RAS?
A most commonly used by GPCR to relay signal
B requires pohsphorylation to be activated
C acts as a GTPase
D acts as a protien kinase
E acgtivated by cAMP

A

OTPION C
monomeric G protein so acts a a GTPase
» needs GTP to be active, not just phosphorylation

51
Q 
What type of cell surface receptor recruits JAK to help initiate signal transduction?
A RTKs (receptor tyrosine kinases)
B G-protein coupled receptor 
C Cytokine receptor 
D GLUT-4	
E Ion channel-linked receptor
A

Cytokine receptor lack intrinsic kinase activity so recruit soluble tyrosine kinase (JAK)

52
Q

where can IP3 receptors be found?

A

mitochondria, ER (allow calcium release) or SR!

53
Q 
During apoptosis, caspases exert effects on target molecules via? 
A Phosphorylation
B Cyclisation
C Proteolysis
D Hydrolysis
E Dephosphorylation
A

OPTION C

proteolysis targeting portiens at ASPARTIC ACID residue sites = proteolytic cleavage

1004 The Dynamic Cell (10 decks)

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