Good article @lesshorrible!
It has been great that you made a difference between eukaryotes, which have a nucleus and cells that do not have a nucleus, like bacteria (prokaryotes).
As you also said, when there is an excess of protein in the body, it can be expelled in the body as urea, being this a substance that can be related to white scum in the urine.
When this happens, it can be related to an excess of protein in the body or other conditions.
God Bless Us Al!
Thank you. Next time please also upvote when you comment. Cheers