It will take too long to explain them here. Some easy way for you get good info about them are:

Go to free online encyclopedia Wikipedia by
1) Typing in, or cutting and pasting : en.wikipedia.org/wiki/Main_Page onto the address box in your browser, then click "go" or simply hit the return key.
2) When you get to wikipedia, type in protein or purine in the search box. and click on "go" or hit return key.

Or, search internet using a search engine such as google by:
1) Typing in: google.com in the address box of your browser and hit return.
2) Typing in protein or purine .

Have fun.