Chapter 6 (part a) Problems
What voltage on side A of a chamber compared to side B (i.e. A - B) would have to be present in order
to make the equilibrium concentration of Ca2+ ions 100 times higher on side A compared to side B? [Hint:
ln(100) = 4.6].
1)
A.
B.
C.
D.
E.
0.059 V
0.118 V
-0.059 V
-0.118 V
0
Under the same conditions as the previous problem (i.e. Ca2+A/Ca2+B = 100 at equilibrium), what would
the equilibrium concentration ratio be for Cl- ions on the A side divided by the B side?
2)
A.
B.
C.
D.
E.
1/10
1/100
10
100
1
3) A) Suppose a cell has an electrostatic potential of -65mV on the inside compared to the outside. If
potassium ions (K+) were at equilibrium across the cell membrane, what would the concentration ratio
of K+ ions be on the outside divided by the inside?
B)
Suppose the cell spends energy to pump K+ from the outside of the cell to the inside. How much energy
in kJ/mol do the pumps have to provide in order to maintain a concentration of K+ that is 200 times
higher inside the cell compared to the outside, while the electrostatic potential difference remains at
-65mV?
4)
Consider a situation where the concentration of protons (H+) is different on the two sides of a bacterial
cell membrane. Let the pH be 6.0 outside the cytosol and 7.0 inside the cell. Suppose furthermore that
there is an electrostatic potential difference across the membrane, with the outside being +0.10V
compared to the inside.
Under the conditions above, what is the molar free energy difference for movement of H+ ions from the
outside to the inside of the cell?
5)
If a positive ion is being pumped across a membrane from side A to side B so that it cannot reach
equilibrium, what effect would this have on A - B?
A.
B.
C.
none
>0
<0