Read the information on this website and make notes:
http://www.s-cool.co.uk/a-level/biology/biological-molecules-and-enzymes
Take a look at these videos
https://www.youtube.com/watch?v=H8WJ2KENlK0
http://ed.ted.com/lessons/activation-energy-kickstarting-chemical-reactions-vance-kite
DNA from the beginning: