bio membranes Flashcards
The major interaction responsible for stabilising the plasma membrane
Hydrophobic interactions
What structural features of the plasma membrane are major contributors to its selective permeability?
Phospholipid bilayer
what type of movement is least possible for a phospholipid in the membrane
Flip-flop
If the temperature in the cellular environment is lowered, the cell responds metabolically to maintain the fluidity of its membrane by
A: Introducing more double bonds into fatty acyl chains of fatty acids.
B: Reshuffling the chain between different phospholipid molecules to produce lipids with two unsaturated fatty acids.
Glycolipids are usually located at the
Outer leaflet of the membrane
The best method for study the properties of integral membrane proteins in the plasma membrane is
Freeze fracture and electron microscopy
Cholestrol what portion is facing the external to the membraen
The polar portion
what dose cholestrol to to the flexiability of the lipid membrane
reduces it interfering with the lipid hydorcarbon chain meaing that it gives stiffness to the membrane
Is cholestrol absent in the plasma membrane of plants
no
to increase fludity of the plamsa membrane
Increase the unsaturated fatty acids in the membrane
what kind of compositions occour at the leaflets of the membrane lipids
diffrent ones
list the compents of the membrane that are amphipathic (hydrophilic/phobic parts)
Integral membrane proteins
Phospholipids
Glycolipids
Membrane steroids such as cholesterol, sitosterol and ergosterol
Diffusion involves the movement of………. molecules.
all states of matter
What is the definition of Selective Permeability?
The ability of the cell membrane to allow some things to pass through while preventing other things from passing through.
what 5 things indicate passive membrane souliblity
Unstirred layer Molecular shape Membrane viscosity Oil/water partition coefficient Solute charge
what is important in determing the rate of solute diffusion
The competitive presence of other solutes
What will happen to animal cell when it is placed in an isotonic solution?
Remain at same size
in a hypertonic soultin a cell will shrink becasue
The concentration of solute is greater outside of the cell so water rushes out of the cell. Osmotic gradient favours water movement out of the cell
An animal cell placed in a hypotonic solution will
Take on water
Gases such as Oxygen and Carbon Dioxide cross cell membranes by the process of
Passive Diffusion
What does diffusion and active transport have in common
They both move molecules across the cell membrane
what are some propities of pores be that channels of transporters
Solute flux»_space;> predicted by passive diffusion
Stereospecific
Inactivated by drugs/inhibitors
what are some exmaples of primary active transport
Glutamine/Leucine exchange
Na+/Glutamine transport
Na+/Ca2+ exchange
Specific transport mechanism, limited capacity and transport affected by competition describes
Facilitated diffusion
What type of membrane transporter moves two species in opposite directions across the membrane
Symporter
What is the definition of the Michaelis constant, Km
Km is the concentration of substrate at half Vmax.
When [S] =Km, then v = ?
1/2 Vmax
what is exocytosis used for
Is used to deliver material into the extracellular space
what is an exmaple of regulated secreation by cells
exocytosis
The Na+/K+ ATPase belongs to the P-type family of ATPases
true/ false
true
how many modes dose Na/K have
5
Na,K-ATPase transport has the binding site for NA,K, ATP and ouabain where
The catalytic subunit
The Na,K-ATPase possesses a …….. stimulated phosphatase activity
K
what dose the Na+/K+ ATPase help to maintain
a stable membrane potential
wherer is the gamma phosphate of ATP transfered to
an aspartyl residue on the catalytic subunit
The Na+/K+ ATPase can utilise para-nitrophenyl phosphate as substrate
true false
True
The ATPase activity can split para-nitrophenyl phosphate to generate para-nitrophenol
The Na+/K+/ATPase is an electrogenic transport protein.
true false
True
The charge imbalance means that the Na pump is electrogenic
For every ATP molecule hydrolyzed by the Na+/K+ ATPase (also referred to as the Na+ pump) what is the ratio of K to NA
3 Na+ ions are transported out of the cell and 2 K+ ions are transported into the cell
Ouabain binds to
To the alpha subunit of the Na pump
why is the beta Na/K ATPase subunit needed
The beta subunit is required for Na pump assembly and stability
beta Na/K ATPase subunit is not glycosylated
true false
false it is heaviely glycosylated
how many isforms of the alpha subinut are there for Na/K ATPase
4
how are alpha subinut Na/K ATPase typically expressed
Alpha subunits are developmentally regulated and expressed in a tissue-specific manner
The alpha subunit of the Na,K-ATPase is phosphorylated by which amino acid residues
Serine
Threonine
Tyrosine
C-peptide induces what
phosphorylation of Na,K-ATPase in an ERK-dependent manner
Phosphorylation of ERK kinase in response to C-peptide is blocked by what
PD 98059
C-peptide increases the abudence of what in the basolateral membrane of renal tubular cells
alpha 1 and beta 1 subunits
Insulin will casue the tranlocation of what in skeltal musceles
Na,K-ATPase subunits to the plasma membrane
in what manner are Beta 1 and Beta 2 subunits expressed in skeletal muscle
fibre type specific manner
what effect dose high-fat feeding have on the alpha 1 and alpha 2 subints
increases the abundance of alpha 1 and reduces that of alpha 2 subunits in skeletal muscle
Facilitative transporters
are energy …
independant
SGLT1 is an example of a
Secondary active transporter
what is the stociomestery of glucose uptake by sodium
2Na to 1 glucose
in what direction do facillative GLUT transporters uptake
in the direction of the solute chemical gradient
SGLT 1 uses what for transport
sodium electrochemical gradient
define saturation
When a group of carrier proteins is operating at its maximum rate
HCO3–/ Cl– transporter is an example of
Antiport
what kind of transporter only carrys one thing
Uniport carriers
what transporters are located on the Basolateral membrane of the enterocyte (gut cell)
GLUT2
Na,K-ATPase
where is GLUT 4 expressed
GLUT4 is expressed in skeletal muscle and adipose tissue
what kind of sensor is GLUT 2
GLUT2 is a glucose sensor
Exercise stimualtes what for GLUT4
translocatino in skeletal musceles
Bumetanide acts to regulate water balance by
Inhibiting the renal Na,K,2Cl cotransporter
Ouabain is a cardiac glycoside. Its effect on heart contraction is due to
Inhibition of the Na,K-ATPase, reduced Na/Ca exchange and increased intracellular calcium in heart cells
define the pump leak hypothesis
the idea that there is a slow movment of Na and K into and out the cell via diffusion
name evidence for the pump leak hypotheis
the use of radiolabbelling Na and K in a soultion
what is the energy source for the Na/K pump
ATP as glucose removal did not inhibit the pump ruling out glycolysis and removal of O2 removed krebs
What kind of trnasporter is the Na/K pump
it is symport as Na goes one way and K the other
what are the five operantion modes of the pump
Normal reverse Na-Na exchange uncoupled Na efflux K-K exchange
Look up the mechanism for actoin for Na/K pump
thoughts
look up strucutre of Na/K pump
thoughts
On the Na/K pump where dose oubain bind
the caylylic subunit
In the Na/K pump what is the funtion of beta units
unique function for skeletal muscle with b1 or b2 expressed differently if the muscle is contracting properties of the muscle fibre and oxidative properties
where are alpha one and two found
alpha one - all issues highest in the kindneys
alpha two - all tissue a lot in the brain and skeletal tissue
What is a basic fact about the Cl ion
negative ion with two stable and one unstabel
the third shell of the Cl accepts the electron
in animal cells what is the Cl concentraiton of the ECF compared to the ICF
larger in the ICF than in the ECF
normal Cl levels in the ICF
5-40 nm depeinding on the tissue
What are the 5 main ClC channel familes
CIC CFTR CaCC VSOAC MAC-1
What are the members of the CIC family
CIC- 1-6 ,CIC-7/Ostm1 as well as hCIC-Ka/barttin and hCIC-Kb/barttin
( barttin and Ostm1 needed for funtion)
what ar the two tpyes of anion channels of the Cl
those found at the plamsa membrane (hCIC-Ka/barttin , hCIC-Kb/barttin , CIC-1,2
and the membrane of intracellular organells (CIC-7/Ostm1 . CIC-3-6)
Describe the double barrled idea found in CIC-0 and shown in others
that the CIC channels show an exact doulbing indiactes that the channel has two identical channels each indepdant of the other
the gating of the Cl channels can be influenced by what
changes in MP with a more + MP increasing the liklehood of the channels opening
What structure do all CICs shows
also homodimeric made up of two identical protomers
what technique was used to investigate neurotrammiter release
high reselution pictures of the nurotransmitter with Taiwan bandit kraits venom
What are mepps
small depolorisation events when measuring the MP
vesamicol was used to investigat mepps how
as vesamicol blocks Ach uptake into the vesicels with addition cuasing a reduction in mepps
How was black widoe venom used to invesitage vesiceles
when measured addition cuased massive relase of mepps then a flatline shows it causes massive release of vesicels
look at the digram for the vesicel life cycle
thoughts
why is Ca essential for neurotransmitter
This Ca will trigger vesicle exocytosis of the vesicels
what effect dose Mg have on neurotranmitters
block the relese of vesicels
define the endplate potentiol (EPP)
it is a MP change that is made up of diffrent units eg all for one
quantal content (QC) is what
is the mean epp amplitude divided by the mean mepp. This will represent the number of vesicles released per nerve stimulus
How will dendrotoxin effect the QC
it will block some K voltage gated channels
causing Ca influx and rasied EPP but not mepps
Tubocurarine will change the ….
reduced epp as it block the ACh receptors as well as the mepp as ther is less space for the Ach to bind
Botulinum acts pre/post synaptically
pre and will reduced the number of vesihels released
read over vesicular release
thoughts
What dose patch clamp allow for
study of single and populations of receptors
name the 4 diffrent types of pacth clamp
Cell attachted
whole-cell
outside-out
insude-out
explain cell attachted patch clamp and give one pro and con
the receptor still attached to the membrane
pro can recrd a singel receptor
con cannot change drug concentratins
explain whoel-cell patch clamp and give one pro and con
suction is increased and it can break the membrane with the recording solution accessing the cell measuring a population of receptors
pro control of intra & extracellular environment
con biochemical washout of the intracellular environment
explain outside-out patch clamp and give one pro and con
when pulling away the membrane will snap with the receptors facing towards the cell
pro can change/ control extracellular drug (agonist) concentrations
cons cannot easily change intracellular environment
explain inside out patch clamp and give one pro and con
cell-attached where it is pulled where the membrane will snap with the receptors facing into the pippete
pro control of intra/extracellular environment
con - cannot easily change concentration of agonist
look at the digrams for all the patch-clamp syuff
thoughts
What did cloning allow for the discovery of
what agonist bind ion channel postions cation vs anion conductence binding site of new drugs shows how releated they were
look up the diffrent subunits for the ACh recepotr
thoughts
what are the two ways to identify Ach receptor subunits
Oocyte expression system (frog)
use epethial cell in culture that do not normally have nAChR
using cDNA to modify them the GFP to ideitfy the nAChR containing cells
describe what α7 5HT3A chimeras have found
allows for the identification of singel channel conductence region on the receptor as well as agonsit binding site
what dose loop C do in ACh binding
binding of ACh stabalies loop C casuing it to close resulting in the confomraitonal change
describe the watering can model
Argaine loops in the 5HT were seen to decrease Na passage happens as 5HT last section Na passes through seen model picture
what sites wil GABBA effect
GABBAa
GABBAb
what is the GABBAa receptor
transmitter gated ion channels with 5 subunits
what is the GABBAb receptor
a hetrodimer with GABBA binding to the B1 and B2 for GPCR coupiling
where is GABBAa located
postsynaps
where is GABBAb located
the post and pre synaps
what is Tonic inhibition
where the extra-synaptic GABBAa receptors that are activated by lower GABBA levels and are constantly being activated resulting in a slow tonic current in response to the GABBA
what is phasic inhibition
When GABBA triggers them (GABBAa receptors) most will open simultaneously but will stay open for different times this causes a curve to the graph this is called phasic inhibition this is often found in the synaptic cleft
What is the effect of glycine and GABBA on MP
Glycine will casue depolorisation and an AP to fire through glutamate cartion channels. GABBA will cause a flow of anion channels to open reducing the depolorisation
what is feed-forawrd inhibiton
after stimulation by the glycine the GABBA will reach the neuron 1-5 msec after casuing the depolorising effect to be reduced
what is feed back inhibtion (GABBA)
the AP from a glutamte will trigger the GABBA internuoron activating the GABBAa and repolorising the membrane
what kind of protein are GABBAb
G protiens receptors coupled to Gαi and Gαo
what dose actvation of GABBAa do
causing Cl channels to open causing an IPSP(inhibitory post-synaptic potential)
What dose GABBA in the synaptic cleft do
then activate the GABBAB receptors causing the βy complexes to disassociate and lower probability for Ca channels to open. This reduces the IPSP
Post synaptic GABBAb activation will casue what
GABBAB post-synaptic causing K+ channels to open causing further & prolonged hyperpolarisation and so a longer IPSP
what effects do Benzodiazepines have on GABBA receptors
increase likleyhood of the receptors opening
pentobarbital (barbituate) dose what to GABBA receptors
increase time of the receptors opening
how many diffrent alpha GABBAa subunits are there
6
Which GABBAa subunits are enchced by diazepam
α1,2,3 & 5
What diffrent in AA was seen in the α1,2,3 & 5 compared to the α4,6 of GABBAa
one AA with H in the α1,2,3 & 5 and a R in the α4,6
what method was used to identify the diffrent effects of the GABBAa a subtypes
knock out mice
what GABBAaR a subypes corrolate to what effect
α1-sedation α2,3- anxiolytic/analgesic (anxiety /painkiller) α5- cognition B3 - immobility/anesthesia B2- sedation/anesthesia
what is a enhancer of GABBA
5α-pregnan-3α-ol-20-one (5α-3α)
5α-3α is found to be synthesised where
in the brain meaing they are called neurosteroids
what conditions casue neurosteroids release
to pregnancy, puberty , stress and epilepsy
what effects to neurosteroids have
anxiolytic (anti-axiety), sedative , hypnotic (get to sleep), analgesic (painkiller), anticonvulsant and antidepressant
what evidence is ther that neurosteroids act through the a2 GABBAaR subunit
konckout mice of the a2 showed increased speed in synaptic events
what are the three diffrent gene familes that act for the glutamate receptor
AMPA, kainite and NMDA
what will the glutamate recepotr trigger
will open causing the flow of Na into the cell resulting in an inward current
What is the NMDAR key propites
conducts NA and is permeable to CA as well as K out the cell and will be blocked by MG needs the co-agonsit glycine
How is the NMDAR blocked by Mg
the Mg will be attracted to the open receptor and bind to its center blocking the flow
What will happen to NMDAR when Mg is at high doses
Chattering will happen with the channel rapdiley opening and shutting as when the Mg binds the depolorisation effect is reduced
What is NMDAR co agonist
agonist glycine or D-serine
How are NMDAR and AMPAR linked
after glutamte stimulation and the NMDAR opening and blockage by Mg. The increased Na will activate the AMPAR causing a depolorisatin of the cell and the Mg to be expelled
What are the effects of NMDAR and AMPAR linkage
casue more NMDAR activation as Mg is removed so a slower depolorisation assosiated with learning
where is the glutamte binding site
S1&S2 domain
look up the way that glutamte receptors are moved to the synaps
thoughts
what can efffect the translocaiton of glutamate receptors
be neuronal activaty, acute/chronic stress, Alzheimer’s and neurodegenerative disorders and drugs eg coke, ket
Long term potentiation (LPT) is assosiated with learning how is glutamte receptor assosiated with this
the stimulation causes depolarisation the spine causing Mg blocking to be removed on the NMDA and more intracellular Ca and this then causing translocation of CaMKII to spines that cause phosphorylation of AMPA receptors causing them to increasing bind to the post-synaptic through diffusion trapping allowing for more LPT
what GLu subunits are related to spacial memory
the GluA1 & 2 subunits for the AMPA
what do mice with huntingtons express
express impaired LTP with AMPAkine (AMPA agonist) improves cognitive performance
define gap junitons
array of intracellular channel that allow for cell to cell communication and comprise of a large number of cells directly and allow for them to “taste” the others cytoplasm as well as with the extracellular space
what are gap juntions made of
connexions
what is an effect of gap juntions
they can alter resistance between cells through the flow of ions
how many connexions make up a gap juntion
6
what are gap juntions peramble to
to inorganic ions K, NA, CL, HCO3 as well as small inorganic signalling molecules (cAMP,IP3), dyes and Glucose
what do gap juntnions do in neurons
they do not generate current fluxes but will pass ions from one to another along the electro-chemical gradient
what is eltrical synpases between juntions mediated by
Cx36 but only 0.1% actually conducts
How were eletrical synapes discovered
through the meauring of escape synapses in shrimp with a MP generated much faster than GABBA or a chemical interface could allow
what is the diffrence in arragment of eletrical and chemical gap juntions
chemical is non-reversible and omnidirectional while the electrical can act in both directions
Gap juntions can be mapped with dye but ..
they are non-reversible so cannot be repeated and the connexions may show specificty
what it the most common way to measure gap juntions
Dual cell electrophysiolog with two neurons placed with the current measured between them
read over all the diffrnces in gap juniotns
thoughts
what are improtant propities of the eltrical networks
Bidirectionally, shorter synaptic delay, sign preservation, mediates hyper and depolrazing responses, helps with generating AP and synchrony( similar responses), coordinates activity of large cell populations
what allows for brain rythmes
gap juntions will only form between similar neuonrs with climbing fibers linking the rest allows for large scale linkage
why do Cx36 knockout mice show night blindess
In the eyes the rods and cone have connexions that connect the cells together with the cones using Cx36 in the KO mice this connection was not longer there meaning that the signal could not be transmitted down to the brain via the electrical synapse and the Cx36
how do Cx36 knockout mice cerabellum differ
the inferior olive of the cerebellum the eletrical synapses that go to the purkinje cells with linkage by the gap juntions. Allows for wave form to be seen normally with KO mice not showing it and impared muscelse with that
what are the two facrotrs that effect K efflux/influx
concentration gradient
eletrical gradient
Why is the MP of a resting cell + than the EP of K
as while K reguatles MP other cahrged ions exist in the cell Na, Cl . The larger + stop K from leaking out and causing changes in flwo of Ca, Cl
How is the effect of an ion determined on a membrane
its permability as changes in permaiblty will casue efflux/influx and a change in the MP
define gating
is wjen the TM S4 with its + charge will be repelled out of the cell casuing a conformational change in the a subunit and the pore to open means that the pore only open when needed eg specific MP
define channel inactivation
causes the blockage of a channel after sustained depolorisation by an IFM see diagram to ensure that there is ont an unctorlled flow
define ion selectivity
it is found at the top of the pore with a collectin of + or - AA as well as a set size acts as a filter to make sure the right things get through
Look at digrams for ion selctivilty channel inacitvaiton and gating
thoughts
How dose Glu account for the gating in CIC
as it is in a + ,- or neutral charge it will bind in three ways with the + charge allowing for conductence this gating can be altered by Ca levels ph
myotonia congenita is what
mutation in the CIC-1 that causes relaxation of skeletal muscele to be hard
A mutation in the CIC-1 will cause what at the transverse tubules
causes the accumilation of K and a depolorising effect that is usally contered by CIC but causes autonomous AP friing
Look at the double barreled structure
thoughts
what are the three tpyes of K channel
6TM 2TM and 4TM
what are the Kv channels responsible for
shaping of the AP
Describe how maxi-K channels are inacivated
20 amino acids that are a hydrophobic “ball” that is at the head of a 50-60 chain of AA blocking the channel
What are the two ways that maxi-K channels are contorlled
through MP and Ca concentration
How dose in maxi-K channels Ca concentration lead to acitvation
Ca will gather in the Ca bowl casuing RCK to undergo conformational change and push on the S4
Look at the diagram for maxi-K
thoughts
TREK and KATP are what kind of channel
TM4 and TM2 K channels Cav channels
What do TREK and KATP help control
they allow for stablisaiton of MP as they are always open so are trying to reach GHK equilibrium -80 in cells repolorises the cells
What do TREK and KATP KO mice show
decreased anaesthetic sensitivity, increased epilepsy and ischemia , increased pain as well as the having anti-depressant qualities
What are two things that maxi-K channels helpl do
for hypertension regulation as well as timing of bursts of AP and contributes to afterhyperpolarisation or the refractory period. It also balances the effect of excess vasoconstriction as it will open due to the excess Ca and then stop the flow of Ca into the cell
How do KATP TM2 channel blockers help in type 2 diabetes
As they are the channel for insulin release via K excoytosis. inhibitors of this channel will causes the ATP to not be released and Ca to flow into the cell casuing insulin release see diagram
define whole cell depolorisatoin
made up of a collection of single channel currents that have the same average current happen at the same time but have different duration and are only open for a short time
why do Na channels and K channels open at diffrent times
to allow for depolorisation to occour
what is cord conductence
the relationship between the voltage current and Ena . flows a vally shape with current increasing as MP increases then drop again as it gets closer to the Ena
how many Nav a subunits are there
Nav1.1-1.9
what is the role of beta subunits in Nav
They help to modulate channel opening for rapid activation/inactivation with a β1 mutation seen in epileptics with the immunoglobulin domains binding to extracellular proteins that help with channel localisation in cells. The Na channels are located at the node of Ranvier
How dose TTX have an effect on Nav channels
It block them form the outside of the channels where it binds to AA residues on the outer mouth of the channel. TTX acts on the glutamate of the P domain as well as for cardiac Na channels on cysteine on the P domain
how do anasthetics lignocaine have an effect
LAs are small lipid molecules that cross the neve sheath and cell membrane to reach the site of action from there they will block the Na from the intieor binding to the - inside Na channels
differential sensitivity of cardiac, CNS and PNS sodium channels to tetrodotoxin happens becauses ..
the diffrent subuints are present in eacjh of the diffrent tiissues as they regulate diffrently meaing there is a altered effect
What is diffrent about Ca to most ions
acts as a chemical signal as well as an eltrical
list the diffrent subunits of the Cav channel
alpha 1, beta , a glycosolated alpha 2 , alpha 2 delta and a gamma
what is the role of the P HVA type subtype in a Ca channe
neurotrasnmitter release
what is the role of the N HVA type subtype in a Ca channel
neurotrasnmitter release
what is the role of the L HVA tpye subtype in a Ca channel
E-C coupling hormone secreation and muscel contraction
what is the role of the Q HVA type subtype in a Ca channel
neurotrasnmitter release
what is the role of the R H/LVA type subtype in a Ca channel
Ca-actin potetniols neurotrasnmitter release
what is the role of the T LVA type subtype in a Ca channel
repetative firing
What effect do GPCRs have on the Ca channel
inhibit the the Ca current PKA will also cuases an increase in the current via phosphoralaytion
name 3 muations in the Ca and effect in the Cav1
hypokalemic periodic paralysis in Cav1.1 in the S4 regions that causes a reduced Ca current and muscle weakness
Timothy syndrome where a Cav1.2 mutations causes loss of channel inactivation with increased Ca entry and with that server cardiac dysregulation
. Night blindness found in the Cav1.4 with reduced transmitter released from the retinal photoreceptor
name 3 muations in the Ca and effect in in Cav2,3
. Autism associated with Cav3.2 mutations
Migraines a Cav2.1 mutation causing increased channel activity and transmitter release and migraines
Ataxia causing attacks of motor dysfunction caused by Cav2.1 mutations that prevent normal channel formation and loss of Ca current
