Proteins as Enzymes Known as a biological catalyst – They are proteins that speed up chemical reactions in living things. Enzymes speed up reactions by lowering the activation energy: – They lower the amount of energy required for a reaction.

Properties of Enzymes They are types of complex proteins (tertiary & quaternary structure) They are not changed by the reactions they speed up (they are recycled) They are SPECIFIC—means that only one enzyme will work with one particular substrate – Substrate: reactants in a chemical reaction

How Enzymes Catalyze Reactions to form Products Active Site: place where substrate bonds Enzyme-Substrate Complex: Formed when substrate bonds to enzyme; bonds are weakened Substrate: Reactant Enzyme: Biological catalyze Product(s): compounds formed by a chemical reaction Enzyme is unchanged and can be used again.

Lock & Key Model of Enzymes Hydrolysis: breaking down polymers Condensation: making polymers

How Sucrase Catalyzed the Hydrolysis of Sucrose Examples of Other Enzymes EnzymeSubstrate AmylaseStarch PeptidaseSmall Proteins LactaseLactose LipaseMost Fats PepsinLarge Proteins

An enzyme may fail to work if it’s environment is changed in some way. If you change the protein’s shape, you change it’s function. Factors that Affect Enzyme Activity In order for an enzyme to work most efficiently, there must be must be the presence of: a sufficient quantity of the enzyme optimal (ideal) temperature optimal pH