acid percipitation lab

[misteeq155]

Hey guys,

 

I have a lab report due in 2 days and there are couple questions i just cant figure out. Its for a 200 level biochem class. The experiment has to do with acid percipitation of protiens. its just a very simple experiment where you percipitate cytochrome c and then milk protiens by the addition of 0.5% and then 20% acetic acid. one of the questions in the report is why does the cytochrome percipitate first when you add the acetic acid but then redissolve with the 2nd addition of the acid...does this have anything to do with the pH/ isoelectric point or am i way off? please if anybody could help me with this question i would really appreciate it.