During diffusion, do molecules move from areas of low concentration to high concentration, or high concentration to low concentration? what about during active transport?

1) Diffusion is the move of molecules from high to low concentration.
Molecules move with the concentration gradient (high -> low) in diffusion until concentration is uniform. One example is osmosis - the movement of water.

2) Active transport is the move of molecules from low to high concentration.
This kind of transport requires energy to move against the concentration gradient (low -> high). Think: being "active" requires energy. 

The basic repeating unit of nucleic acids are known as nucleotides. a nucleotide consists of three distinct chemical groups.