Membrane Potentials Flashcards
Potential Difference Definition
The difference in charge between two points
measured in voltmeters (mV)
How is Potential Difference Measured
using a voltmeter. it has two leads that measure the volts shown on the display screen.
Membrane Potential Definition
- formation of electrical gradient between the inside and outside of the cell
- potential difference across the membrane
- varies from cell to cell
- can be affected by membrane transport
How can you measure Potential Difference?
By placing a cell with low intracellular conc. of substance [x] (monovaent catoin) into an extracellular fluid with a high conc. of substance [x]. if ion channels are opened, substance [x] would flow down conc gradient into cell causng a more positive membrane potential. Measured by placing a microelectrode on either side of the plasma membrane
Equilibrium Definition:
no net movement of ions in or out of the cell
Valency Definition:
refers to the ion’s combining power with other substances
Anion Definition:
A negativley charged ion
Cation Definition:
A positivley charged ion
Concentration Gradient Definition:
the difference between conc. of solutes on either side of the membrane.
intra vs extracellular conc.
Electrical Gradient Definition:
difference in charge of ion across the membrane
Why we only consider what is happening inside the cell when studying effets of ion movement across the membrane?
Extracellular fluid contains a very large quantity of fluid. Small ionic changes don’t register a change. Therefore, extracellular environment is always considered as 0
How are we able to predict the polarity of the membrane potenital if we know what ion channels are open and the relative concentration of these ions inside and outside the cell.
when provided with:
1. intra and extracellular concentrations of a cell
2. which channels are open
3. the ion movement direction across plasma membrane
AND
4. the consequent change to intracellular environment
This indicates the polarity of a membrane
Magnitude of membrane potenital is directly proportional to..?
…the size of the concentration gradient of ion movement across the membrane
Equilibirum Potential Definition
The potenital difference across the membrane that will exist after equilibrium has been reached
Nernst Equation is uesd for:
allows us to calculate theorectical value of membrane potential in a cell which is selectively permeable to one ion species
