2.4 Chemical Reactions and Enzymes
Lesson Objectives
-Explain how chemical reactions affect chemical bonds.
-Describe how energy changes affect how easily a chemical reaction will occur.
-Explain why enzymes are important to living things.
Lesson Summary
Chemical Reactions Everything that happens in an organism is based on chemical reactions. A chemical reaction is a process that changes one set of chemicals into another set of chemicals.
-The elements or compounds that enter into the reaction are the reactants.
-The elements or compounds produced by the reaction are the products.
-Chemical reactions involve changes in the chemical bonds that join atoms in compounds.
Energy in Reactions Some chemical reaction release energy; others absorb energy.
-Chemical reactions that release energy often occur on their own.
-Chemical reactions that absorb energy require a source of energy. The energy needed to get a reaction started is called the activation energy.
Enzymes An enzyme is a protein that acts as biological catalyst. A catalyst is a substance that speeds up the rate of a chemical reaction. Catalysts work by lowering a reaction’s activation energy.
-In an enzyme-catalyzed reaction, the reactants are known as substrates. Substrates bind to a part of an enzyme called the active site and remain bound to the enzyme until the reaction is complete, when the products are released.
-Temperature, pH, and regulatory molecules can affect the activity of enzymes.