Energy is a page from the CHEMystery web site that includes such topics as energy, matter and energy, and the law of conservation of matter and energy. This site is geared toward the high school student but is highly useful for anyone.

http://library.advanced.org/3659/energy/

The Molecular Structure of Enzymes, a site by Richard Hallick of the University of Arizona, shows the structure and action of enzymes. Choose "catalysis" for an explanation of enzyme action.

http://www.biology.arizona.edu/181/rick/energy/enzymes2.html