Question

How are proteins distinguished from each other?

Answer 1

It depends on the context.

Explanation:

You can take an inside-out approach and compare the sequences directly if they're known for both proteins.

Or, if you don't know the sequences, you can sort them by their physical properties - for example, if one protein is larger than another, it will migrate through a gel slower. So you can run them on a gel, small proteins come out first, big proteins come out later.