Rudolph Marcus, a Canadian-born American chemist who received the Nobel Prize in Chemistry for developing a theory that helped explain the electrochemical processes behind photosynthesis, respiration, oxidation and even how fireflies produce light, died on July 17 at his home in Pasadena, CA. He was 102.

Sarah Reisman, chair of the chemistry and chemical engineering division of the California Institute of Technology, where Dr. Marcus had taught since 1978, said that it was almost impossible to state the importance of Dr. Marcus’s work. “It provides a simple theory for one of the most fundamental processes in chemistry, and has been applied to understanding reactions ranging from small-molecule catalysts to proteins involved in photosynthesis,” she said.

Dr. Marcus received dozens of awards, among them the Wolf Prize, considered to be the most prestigious award in chemistry after the Nobel, and also the esteemed National Medal of Science.