what are the steps in protein breakdown using electrophoresis?

Answer 1

They do not break down.
What type of electrophoresis do you refer to?

I assume you are asking how proteins are separated by using electrophoresis.

During electrophoresis charged protein molecules are forced to move towards one of the electrodes through a gel.
They will run with different velocities depending on the condtions of the experiment, the size, shape, charge of the molecule and the concentration of the gel (determines how big are the gaps in the gel so that the protein molecules can move).

In SDS-electrophoresis proteins are completely denaturated and thus shape doesn't play a role any more. This also means that if your protein is an oligomer with this type of electrophoresis you will see the monomer only, unless denaturation is not complete.
You have approximately 1 SDS molecule (which has negative charge) for every 2 amino acids. Thus the molecule gets a very high negative charge which is also as you might guess a function of the size (more amino acids, more SDS molecules, thus more negative charge).

This way the proteins are more or less running according to their size (bigger move slower because it is hard for them to travel through the gel). There are always exceptions especially when dealing with post-translationaly modified proteins like phosphorylation and glycosylation. Then proteins could run faster or slower from what expected.

There are more types of electrophoresis like that under native conditions where all the above factors take place and you can see for example even oligomers.

You also have isoelectric focusing where the pH of the gel is a gradient instead of having a constant value. Then proteins move until they reach the point of the gel that the pH is such that the net charge of the protein is 0. Then electric field can't apply a force on the protein and the protein doesn't diffuse away because movement to any other direction will mean change in the pH of the gel giving again a net charge to the protein and forcing into move according to the electric field

Formulate your question better so that we can answer properly

Answer 2

they shouldnt break down in the process! electrophoresis is for separating different protein types from each other

typically the most common PAGE - polyacrylamide gel electroproresis
1. prepare sample of denaturalized protins covered by detergent (SDS)

2. mount the sample on loosely polymerized stacking gel where the porteins are positioned in narrow belt

3. they get into the thicker, resolving gel where they are separated because the biggfer molecules move more slowly than the smaller.

be careful as the monomeric acrylamide that the gels are made of is a neurotoxin and the concentration that you use are quite high.