Here are some good YouTube videos by a teacher of biology from the US.

http://www.youtube.com/watch?v=QwDy4rUU5Xw Carb's Part 1

http://www.youtube.com/watch?v=eeMUQnAme5E&feature=related Carb's Part 2

http://www.youtube.com/watch?v=yFRP1tau8HM Lipids

http://www.youtube.com/watch?v=mUVIHmO-lm8&feature=related Proteins

http://www.youtube.com/watch?v=-lUAjoMWtDA Energy and Laws of Thermodynamics