Learning Objectives Define the following terms: enzyme, chemical reaction, reactant, product, activation energy, catalyst, enzyme-substrate complex. Describe how a catalyst will affect the activation energy.

Enzymes and Chemical Reactions

Chemical Reactions CO2 + H2O H2CO3 A chemical reaction is a process that changes or transforms one set of chemicals into another. CO2 + H2O H2CO3 Carbon Water Carbonic acid Dioxide Reactants Product

Reactants O2 + 2H2 2 H2O Reactants - elements or compounds that enter into a chemical reaction.

Products O2 + 2H2 2H2O Products - elements or compounds produced by a chemical reaction.

Chemical Reactions CO2 + H2O H2CO3 Carbon Water Carbonic acid Dioxide Chemical reactions always involve changes in the chemical bonds that join atoms in compounds. These reactions require energy.

Activation Energy Energy Activation Energy Reactants Products Course of Reaction Activation energy - the amount of energy required for a chemical reaction to get started.

Stop Here

Activation Energy Products Activation energy - the amount of energy required for a reaction to get started.

Enzymes A catalyst is a substance that speeds up the rate of a chemical reaction. Catalysts lower the activation energy.

Enzymes are specific Reactant (substrate) Enzyme Enzymes are proteins that act as biological catalysts. Enzymes are very specific, generally catalyzing only one chemical reaction.

Enzyme-Substrate Complex Substrates - reactants of enzyme-catalyzed reactions substrate Enzyme- Substrate Complex Products Chemical Reaction Enzymes provide a site where reactants can get together to complete a chemical reaction, thus reducing the activation energy.

Enzymes Enzymes lower the energy needed (activation energy) and speed up the chemical reaction.

Enzymes can be reused over and over again!

Function of Enzymes Regulating chemical pathways Making materials that cells need Releasing energy Transferring information

Regulation of Enzyme Activity Denatured Enzyme pH Temp Ionic strength Solubility The active site of the enzyme changes shape and can no longer bind to the substrate