Hi, I am struggling to understand this worksheet my professorgave us for practice. Could someone make any sense of this?
The scenario: Sodium is found largely in the extracellularcompartment with concentrations between 130-145 mM withintracellular sodium concentrations between 3.5-5mM. This chemicaldifference gives sodium a large concentration gradient, which whenpermitted (by opening of a channel or through facilitatedtransport) will move down its concentration gradient to enter thecell. Sodium also has a favorable electrical gradient; the cellularmembrane potential sits at -70mV with the extracellular spacesitting at 0 mV. Sodium being a cation, also has an electricalgradient that favors the inward movement of sodium when permitted.If we were to let sodium freely permeate across the cell membraneit would settle at its equilibrium potential where the two forcesequally oppose each other. This value is +66mV, sodium would stillhave a favorable chemical gradient, but an unfavorable electricalgradient. At this point net inward movement down the chemicalgradient would equally oppose the net outward movement downsodium's electrical gradient. Answer the questions below based onthe above information:
ANSWER CHOICES: chemical gradient, electrical gradient, chemicaland electrical gradient, equilibrium point
1. if a cell has a membrane potential of -90mV and sodium isallowed to permeate across the cell membrane, which gradients wouldsodium be moving down? Â
2. if a cell has a membrane potential of -10mV and sodium isallowed to permeate across the cell membrane, which gradients wouldsodium be moving down?
3. If a cell has a membrane potential of 0 mV and sodium canpermeate the cell membrane, which gradients would sodium be movingdown?
4. If a cell has a membrane potential of +66 mV and sodium isallowed to permeate across the cell membrane, which gradients wouldsodium be moving down?
5. If a cell has a membrane potential at +90mV and sodium isallowed to permeate across the cell membrane, which gradients wouldsodium be moving down?
6. Out of all the above scenerios, which membrane potentialwould yield the highest net rate of Na+ transport? The lowest?
