In EK, Chapter 7, it says 'electrophoresis uses an electrolytic cell. It is important that neg charged AAs within the electrolytic cell flow toward the positive electrode, so the anode is labeled positive in the electrolytic cell." What exactly are they trying to get at? Are they saying that the labels are arbitrary? Why do the Amino Acids flow to the anode anyway? What makes it more positive?
I posted this in another thread about a similar question, but here is what works for me:
ACID: Anode Current into Device. ALWAYS. In a galvanic cell, this is where current flows back into the device/cell. Remember that electrons go the opposite way because Ben Franklin picked the wrong sphere. So, at the anode of a galvanic cell, current goes in, electrons come out.
Of course, an electrolytic cell is the opposite (as if you were recharging a battery). So, current would flow into the 'positive' terminal of the cell, and electrons would leave from there, making that the anode instead.
CCD: Cathode Current Departs. The last mnemonics to remember are probably RED CAT and AN OX, indicating the process(es) taking place at each electrode, respectively. Reduction at cathode (if current departs, electrons come in...and gaining electrons is reduction), oxidation at anode (if current enters, electrons go out...losing electrons is oxidation).
Your negatively charged AAs (based on a combination of their side chains + pH, as you need to see what's been deprotonated at a given point) will be attracted to the positive end and travel happily towards the anode. SDS could be added to, IIRC, glob up charge relative to the size of the AA on the amino acid, and again IIRC, mercaptoethanol is added to cleave disulfide bonds from cysteine.
