Why does the Milk Curdle when I add Vinegar?

Well, I knew that I had to answer this question, but seriously, the chemical bonds and everything look so complicated. Seriously, I went on this site: http://www.itisacqui.it/sitob/formagette/curdling.htm to find out what happens, but it's so hard to understand. ;-;
Anyway, I might ask Ms Zhang for help on it ^^''
Until then, I have a diagram. Of casein.

I'm not gonna lie, I have NO IDEA as to what the labels on the picture are.
All will reveal itself in the due course of time... 

Anyway, I went on yahoo answers and google to try and find out the answer to the question that is on the title of this post.
I'm not even sure if we're allowed to use yahoo answers. LOL.
Ah well, I'll just trust the people with a professional looking profile picture. AHAHAH.


One person said "The hydrogen ions from vinegar (5% water solution of acetic acid) react with -NH2 groups of lysine and asparagine to clot the milk and drive proteins out of solultion."
Um, yeah, so what is lysine, asparagine (related to asparagus?) and MINUS NH2? I understand the NH2 part but why the minus?!! There was also a typo in 'solultion'. Now I know why teachers don't like yahoo answers.

On to the next website. A cooking website. Don't you just love my variation in sources. Not. I should be using books or something shouldn't I? Too bad, it's the 21st century
According to Shirley Corriher on  http://www.finecooking.com/why-vinegar-curdles-milk.aspx "Acid on protein causes the protein to coagulate, because the acid is actually "cooking" the protein strands. When vinegar curdles milk, what you get is a dairy version of scrambled eggs." and that "When in doubt, a little cornstarch is always good insurance to prevent curdling."
Well, at least I can understand this answer... No, I still don't know what "coagulate" is. Why isn't this taught in school? -cries- Anyway, next time I am going to do the following because I'm really tired right now and need a shower:

• Find out why milk curdles when I add vinegar? (what I should have answered here)
• Learn what coagulate is
• Ask Ms Zhang for help
• Try and find more stuff on what happens when I add more vinegar to my milk (there are seriously NO websites with this!!!)