Check out the Help Videos Below!
Click on the following links from Khan Academy:
Cellular Respiration: https://www.khanacademy.org/science/biology/cellular-respiration-and-fermentation
Scientific Notation: http://www.khanacademy.org/math/algebra/exponents-radicals/v/significant-figures
Scalers and Vectors:
http://www.khanacademy.org/science/physics/mechanics/v/introduction-to-vectors-and-scalars
The Atom:
http://www.khanacademy.org/science/chemistry/introduction-to-the-atom