Electrochemical gradients Flashcards
what are cell membranes made up of
glycerophospholipids
bilayer
prevents movement of charged molecules
how does the cell membrane prevent the movement of charged molecules
extremely high resistance to the passage of current
gases and small amphiphilic compounds can diffuse easily
3 types of membrane proteins that enable charged molecules to cross the membrane
gap junctions
electrical synapses
membrane transporters
gap junctions
large pores that from between adjacent cells
can pass ions and small molecules
electrical synapses
specialised form of gap junctions
membrane transporters
integral membrane proteins that mediate facilitate diffusion or active transport
aka pumps
2 forms of active transport
primary
secondary
primary active transport
utilises an energy source
secondary active transport
uses the ion gradients established by primary active transport processes
3 types of membrane transporters
uniports
symports
antiports
uniport
transports single molecule
symports
moves multiples molecules in the same direction
antiports
move multiple molecules in opposing directions
channels
allow water or ions to flow rapidly through a water-filled pore
key properties of channels
represent a direct connection between intra and extra cellular spaces
move small molecules
always move charged molecules down concentration gradient
passive
dissipate concentration gradients
extremely high speed
pumps
never any connection between intra and extra cellular spaces
can move larger molecules
by using ATP anti ports can move molecules against their concentration gradients
build up concentration gradients
slower
what is membrane potential
difference in electrical potential between the interior and exterior of a biological cell
typical membrane potential value
+40mV to -70mV
Vm
potential difference
movement of one positive ion from the outside to the inside results in +2mV change in Vm
depolarisation
movement to a more positive membrane potential
hyperpolarisation
movement to a more negative membrane potential
inside of cell
more negative than the extracellular environment
due to cells permeability to certain ions and the numbers of those ions
Na+ intra and extra cellular concentration
E;145
I: 12
K+ intra and extra cellular concentration
E: 4
I: 120
Cl- intra and extra cellular concentration
E: 110
I: 15
Ca2+ intra and extra cellular concentration
E: 2.5
I: 0.0001
principle intracellular cation
potassium
principle extracellular cation
sodium
principle anion
chloride
mainly extracellular
resting potential
no active stimulus
equilibrium potential across cell membrane
0
mammalian neurone equilibrium potentials for Na+ and K+
Na= +60
K= -88
calculating the reversal potential for an ion
using the Nerst equation
calculating the reversal potential for a mammalian neutron at 37 degrees
resting potential
-70mV
sodium potassium pump uses ATP to move 3 Na+ out and 2K+ in
creates negativity inside of the cell
leaky potassium channels to allow the K+ to diffuse out
cell is said to be polarised
action potential generation
in the presence of a stimulus
sodium channels open
sodium ions move into the cell and the membrane is said to be depolarised
-70 to +40
when does an action potential occur
threshold potential
what happens when the threshold potential is reached
action potential is generated
opens all sodium channels
more sodium ions move into the cell
action potential moves along the entire length of the membrane until the entire membrane is depolarised
increasing Vm past the threshold
can cause action potential in certain tissues like nerves
repolarisation
once action potential is generated the Na+ close and K+ open
allows K+ to move out of the cell and recreates negativity inside the cell
hyperpolarisation
if membrane potential becomes more negative than the resign membrane potential
no new action potential can be generated
refractory period
no new action potential can be generated
how does the cell return to resting potential l
sodium potassium pump
hypokalaemia
more potassium ions leak out of the cell during resin state
changes membrane potential to more negative value of -90
efflux of positive ions
cell membrane will become hyper polarised
influx of positive ions
cell becomes depolarised
generate action potentia l
hyperkalemia
elevated plasma K+ concentration
effects of changing K+ concentration
effects the resting potential
ability of neurons and muscle cells to reach their action potential
increased K+ causes
increased intake
decreased renal elimination
renal failsure
adrenal disease
medications that alter kidney function
ACE inhibitors
ARBs
potassium-sparing diuretics
NSAIDs
increased release from intracellular stores due to tissue damage
effects of high potassium on the body
irregular heartbeat
chest pain
weakening pulse
kidney conditions
muscle weakeness
changes in mood
shortness of breath
heart palpitations
nausea,vomiting and diarrhoea
numbness or tingling
normal k+ range
3.5-5
hyperkalemic value
7
what does hyperkalemic value do to the EK value
-90 to -83
cells depolarise
RMP closer to action potential
cells easily excited
most life threatening consequence of hyperkalemia
arrhythmia and/or cardiac arrest
due to depolarisation of resting potential cardiac myocytes
