Cell Signalling And Pharmacology Flashcards
True or false?
PI3 kinase phosphorylates PIP2
True
PIP2 -> PIP3
True or false?
PI3 kinase phosphorylates and activates PKB
False… Why : PI3 doesn’t activate PKB. It facilitates the activation but doesn’t activate it DIRECTLY
>Only PKD1 does this
True or false?
PTEN phosphorylates PIP3 to shut down the Signalling pathway
False…PTEN is a phosphatase so REMOVES phosphate to form PIP2
It is a regulatory enzyme
True or false?
Molecules use pleckstrin homology (PH) domains to bind to PIP 3
True. PDK1 and PK-B has PH with PIP3 and then PDK1 activated PKB because of this closeness
Can calcium move through gap junctions?
Yes it can (waves of calcium… Perhaps the same as the ovum/embryo…….
True or false?
Calcium ions can indirectly exert its effects by binding to calmodulin
this is true
Calmodulin has 4 Ca2+ binding sites and undergoes conformational changes when bound.
Name stores of calcium
Sarcoplasmic recticulum, mitochondria and ER!
In paracrine signalling, the signalling molecule…
Acts on cells in close proximity to the secreting cell
So travels a short distance only
True or false?
In response to a signal, the cell can alter RNA transcription
This is true! Cell Signalling controls all biological events including RNA transcription
True or false?
Most signal receptors are found on the cell surface and bind to hydrophobic signalling molecules
False…. Why? First half is true but molecules are. HYDROPHILIC for extracellular signalling
Water soluble so can’t cross lipid bilayer
How do paracrine signalling molecules stay close to their point of origin?
give an example of such molecule
They have limited travel ability as they are easily degraded and inheritably unstable and quickly demobilised
e.g. Histidine or nitrous oxide
Cancer cells produce molecules to stimulate their own growth.
Which class of intercellular communication does this represent?
autocrine
paracrine
endocrine
Autrocrine signalling.
Cells have receptors for that molecule on themselves
What type of signalling molecule is Ras? A. Guanine exchange factor B. Protein kinase C. Protein phosphatase D. GTPase E. None of these
Option D please.
All momomeric G proteins are GTPases!
It needs option A
Why do cell surface receptors use signal transduction pathways?
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.
Which of these are not intracellular secondary messengers? A. cGMP B. ATP C. inositol triphosphate = IP3 D. Diacylglycerol = DAG E. cAMP
Option B please.
ATP is not a signalling molecules. It is used to derive energy. Same with GTP!
True or false?
GEFs increase the GTPase activity of G protein
False… Why? They do GDP back to GTP so don’t degrade/hydrolysed the GTP
> GTP-ase activty = breaking down the GTP
In GPCR (gprotein coupled receptor) signalling, GTP binds to…
alpha
beta
gamma
The alpha subunit of trimeric G protein
Only the alpha subunit has GTPase activity
Ture or false
Cholera toxin modifies galpha S protein class
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
Which mechanisms can terminate intracellular signalling pathway
Degradation of extracellular ligand
Internalisation of activated receptor
Desensitisation of receptor
Deactivation of a signal transduction protein
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
Option D
Plants only have a handful of GPCR
True or false ?
Cryptochrome is a chromophore. Found in blue light receptors
This is true
True or false?
Phytochromes are intracellular receptors that detect light
True
True or false?
Ethlyene receptor is deactivated by ethylene binding
True. Whe ethylene binds, the receptor is inactive, this stops the DEGRADATION of transcriptional regulator
So transcription of ethylene responsive gene can occur
True or false?
Auxin receptors activate transcription factors to drive gene expression
This is false. Auxin receptors affects the repression proteins to remove it!
They don’t ‘t directly affect transcription factors
What is a defining cell feature of dying cells in response to tissue damage (necrosis)
the cell swells
Also a reversible process
cell features of Apoptosis
Cell shrinks
early changes are irreversible
Chromatin condense and fragments, small membrane bodies released and engulfed by other cells (apoptopic bodies)
What is a feature of juxtacrine signalling?
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
describe ways in which calcium stores can increase or decrease
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!
how does the alpha subunit of a trimeric G prtotein work?
dissociates from the beta and gamma subunits.
binds to an effector molecule which then amplifies or inhibts the signal
how do Cytokine receptors differ from receptor tyrosine kinases?
they lack the intricnisc kinase activity so must RECRUIT soluble tyrosine kinase (janus kinase)
give an example of electrical signalling in plants
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
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
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
What dephosphorylates an active protein?
phosphatases
Post Translational modification involves adding chemical functional groups to proteins. Name an example of this?
“Phosphorylation
Acetylation
Methylation
Hydroxylation”
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)
OPTION D cAMP decreased (as adenyly is inhibited) > class i for inhibition!
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
agonist
Adrenocorticotropic hormone (ACTH) travels through the bloodstream, enters connective tissue spaces, and attaches to specific sites on target-cell membranes. These recwptors are
transmemebrane receptors
Ras structure and signalling is a monomeric G protein and is commonly activated by RTK’s. When is it active
when bound to GTP
Phospholipase C is activated by which class of trimeric G protein?
G alpha q class
How is cAMP produced ?
by the effector enzyme adenylyl cyclase which converts ATP to cAMP
How would termination of the cell signal by removing the activated receptor from the cell membrane be achieved?
endocytosis
other ways of terminating signal cascade are to
>eliminate signalling molecule - Achesterase
> deactivate signal transduction proteins (e.g. PTEN)
What moelcule phosphorylates an inactive protein to make it active?
What would it be if it were a lipid?
protein kinase (exception glycogen synthase) lipid kinase!
Which molecule is used to dephosphorylate PIP3 to PIP2
PTEN - the phosphatase
The most well studied receptors with intrinsic enzyme activity are the receptor tyrosine kinases (RTK’s). In order to activate RTK’s it:
Has a kinase that phosphorylates tyrosine’s on opposite receptor tail ie: transphosphorylation.
if a cell loses its function of PTEN what can happen?
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
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
OPTION D
> there is LESS flippage as apoptosis ain’t happening BUT, it flips to the outerleaflet
more proliferation so MORE respiration is happening
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
C is false statement!
INCREASED apoptosis linked with degenerative disorder
> as we lose too many cells
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.
OPTION D
> modifies the Galpah S subclass -> confromation of GTP permenatly active -> more cAMp -> salt and water loss -> cholera/ diahorrea/ dehydration
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
OPTION A
> auxin receptors are ubiquinated to target the protein (auxin hormone) for degredation
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
OTPION C
monomeric G protein so acts a a GTPase
» needs GTP to be active, not just phosphorylation
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
Cytokine receptor lack intrinsic kinase activity so recruit soluble tyrosine kinase (JAK)
where can IP3 receptors be found?
mitochondria, ER (allow calcium release) or SR!
During apoptosis, caspases exert effects on target molecules via? A Phosphorylation B Cyclisation C Proteolysis D Hydrolysis E Dephosphorylation
OPTION C
proteolysis targeting portiens at ASPARTIC ACID residue sites = proteolytic cleavage
