On your results paper you got from ATI it should have at the very end a list of everything you missed and need to study further. I used that list to focus on my problem areas. I also found a friend who knew chemistry and had him tutor me for a day until I understood it!
I went from getting a 54% the first time to an 83.33% on the second try! So huge improvement!
Go to the library and pick up Biology for dummies, it basically goes over plant science and life science. That's all I needed for the TEAS V.