3. The cytosol of a plant cell is more acidic than normal due to
a malfunctioning H+ pump in the membrane. You want to try to fix
this problem by introducing a H+ channel into the membrane of the
cell. (1) Describe the signals that are necessary in the amino acid
sequence in order for the H+ channel to span the membrane 4 times
with the amino terminus on the outside of the cell. (2) Explain the
electrochemical gradient that must exist in order for H+ to diffuse
out of the plant cell through this new H+ channel. (3) How could
this channel be regulated to open only when H+ needs to diffuse? (6
pts)

4. As we learned in class, normally channels are specific and only
allow diffusion of one ion. However, acetylcholine is a
neurotransmitter that opens a ligand gated channel that allows both
Na+ and K+ to diffuse through it (Always an exception!). The
overall effect is a more positive membrane potential. Explain why
this would occur. (Veq for K+ is -90mV and Veq for Na+ is +60mV.)
(2 pt)