Science, Tech, Math › Science Substrate Definition in Chemistry and Other Sciences Share Flipboard Email Print In this example of antimony deposited on metal, the metal acts as a substrate. Cultura/M. Suchea and I.V. Tudose, Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated March 11, 2019 The definition of "substrate" depends on the context in which the word is used, particularly in the sciences. Definitions of Substrate Substrate (chemistry): A substrate is the medium in which a chemical reaction takes place or the reagent in a reaction that provides a surface for absorption. For example, in the fermentation of yeast, the substrate the yeast acts upon is sugar to produce carbon dioxide. In biochemistry, an enzyme substrate is the substance the enzyme acts upon. Sometimes the word substrate is also used as a synonym for the reactant, which is the molecule consumed in a chemical reaction. Substrate (biology): In biology, the substrate may be the surface on which an organism grows or is attached. For example, a microbiological medium may be considered a substrate. The substrate may also be the material at the bottom of a habitat, such as gravel at the base of an aquarium. Substrate may also refer to the surface on which an organism moves. Substrate (materials science): In this context, a substrate is a base on which a process occurs. For example, if gold is electroplated over silver, the silver is the substrate. Substrate (geology): In geology, substrate is underlying stratum.