Is LP based on your win/lose ratio?

Been playing ranked for the past few months and wondered how LP and MMR worked. Some games I receive 23-25 LP, and others I receive 13-14LP. Then in turn to gaining 13-14 LP if I lose, I lose 22-24. I ended up getting put into iron due to being grouped with a support that ran up to Top, 3 times in a row. (I play ADC) Anyway, any feedback would be appreciated. [slayer-pantheon-thumbs]