Anabolic reactions  - this is when simple molecules combine to from more complex molecules. They usually require energy.

Background material reference: http://www.rsc.org/Education/Teachers/Resources/cfb/metabolism.htm

Animation - giving some examples and explaining what is happening

Synthesis of starch using enzymes - Example how potatoes make starch.

http://www.nuffieldfoundation.org/practical-biology/enzyme-catalysed-synthesis