C)
EK+ = -61.5 mV,
ECa++ = +123 mV (did you forget to divide by z which is 2 for calcium?),
ECl- = - 61.5 mV
Helpful Reminder: Log10 of 1
= 0
Log10 of 10 = 1
Log10 of 100 = 2
Log10 of 1000 = 3
#1. See your Textbook!! Pages 177 - 190.
#2. The Nernst Equation (see Toolbox on page182) is :
Vm = (RT/zF) ln [Ion]side1/[Ion]side2
where R = gas constant (8.314 joules/deg mole)
T = degrees Kelvin;
z = valence or charge;
F = Faraday's constant (96,500 coulombs/mole)
At a body temperature of 37oC, and plugging in the constants and converting to log10, the equation becomes:
Vm (in mV) = (61.5/z) log10 [Ion]1/[Ion]2
So ENa+ = +61.5 mV ( inside of cell positive
since Na+ moves in, down C)
EK+ = -61.5 mV,
ECa++ = +123 mV (did you forget to divide
by z which is 2 for calcium?),
ECl- = - 61.5 mV
#3 a. increase P of sodium or calcium or decrease P of potassium or chloride
b. increase P of potassium or chloride (if Vm did not = ECl-) or decrease P of sodium or calcium.
c. increase potassium inside
or decrease it outside
decrease sodium outside or increase it inside
increase calcium outside or decrease it inside
d. reverse of "c" above
(Parts of question 3 assumes that each ion is somewhat permeable and that Vm does NOT = the equilibrium potential for that ion.)
#4a. At threshold (depolarization caused by stimulus or signal molecule), voltage-gated sodium channels open and membrane depolarizes, opening more channels. Sodium channels inactivate (close). This, combined with the opening of voltage-gated potassium channels (caused by depolarization due to entry into cell of sodium), causes repolarization. Cell may briefly hyperpolarize due to Vm going to equilibrium potential of potassium which is more negative that Vm. You should understand why this is so!
d. See your text!!!