HW7

1. Calculate the change in Gibbs Free Energy required to transport a mole of potassium ions from the inside to the outside of a membrane (negatively charged on the inside) having a potential difference of 70 mV. Comment on whether this transport would spontaneously occur.

2. For cation concentrations that are 80 times more concentrated on the inside (than the outside) of a cell, calculate the membrane potential (in volts) that would be required to effectively balance and to maintain this concentration difference. Discuss how or whether this potential difference would change with the charge of the cation (e.g. +1 vs +2 cation). Draw a diagram that illustrates how this balancing occurs.

3. Text, Chapter 12, problem 69.

4. Given these biochemical reduction potentials:

Pyruvate      +     2 H⁺ + 2 e^- -->   Lactate           E'_o = -0.19V
NAD⁺         +    H⁺    + 2 e^-    --> NADH           E'_o = -0.32 V
Calculate the change in Gibbs Free Energy for the reduction of pyruvate by NADH:
        Pyruvate    + NADH    +    H⁺   -->    Lactate + NAD⁺