1.) 由 ... 组成 (yóu ... zǔchéng)
2.) 作为 (zuòwéi)
My Chinese teacher was trying to explain the subtleties with them, but she was doing so in Chinese, which wasn't helpful when I had to try to understand the Chinese in addition to the grammar. Anyway, she was saying something like how 由 ... 组成 is used in very specific contexts, and how it sounds weird in other contexts? And how 作为 requires more information to make the sentence sound "complete". I don't fully remember what she was saying.
If someone could describe the functions and connotations of each structure, that would be excellent. (Is it that 由 ... 组成 can only take a certain class of words after it or something?) I also have a linguistics background, so syntax and the like are welcome, as well.