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Section 2-4 Chemical Reactions and Enzymes chemical reaction: a process that changes or transforms one set of chemicals into another 6CO2 + 6H2O Reactants C6H12O6 + 6O2 Products ***Chemical reactions always involve a change in the bonds that join atoms in compounds*** Enzymes Speed Up Chemical Reactions By Lowering The Activation Energy Activation Energy: The energy needed to get a reaction started Catalyst: speed up the rate of a chemical reaction by lowering the activation energy. Enzymes: proteins that act as biological catalysts in cells Enzymes- Special Proteins • Enzyme- protein that acts as a catalyst • Catalyst- Speeds up reaction but is not used up in reaction • Lowers activation energy Structure of Enzymes • Made of Proteins and a Coenzyme • Active Site- part of molecule involved in reaction • Substrate- reactant being catalyzed Enzyme Activity Products Active Site Enzyme EnzymeSubstrate Complex Enzymes are specific to the reaction they are involved in • Enzymes are shaped specifically for the substrates with which they react • Act like a lock and key • Enzymes can be reused, but will eventually denature Enzymes are affected by many variables • Enzyme effectiveness changes under different conditions • Temperature, pH, and enzyme or substrate concentration all affect how well an enzyme works What is pH? A water molecule can react to form ions Other molecules can also form ions pH Scale: an indication of the concentration of H+ ions in a solution. • pH 7: Neutral • pH <7: Acid (higher H+ concentration) • pH >7: Base (lower H+ concentration)