2 Chemical reactions are taking place all the time. Chemical reactions change substances into different ones by breaking and forming chemical bonds
3 6CO2 +6H2O+light energyC6H12O6 + 6O2 Reactants are the starting materialsThe newly formed substances are called products, which are in general different from the reactants.Reactants on the left Products on right.For example:6CO2 +6H2O+light energyC6H12O6 + 6O2ProductsReactants
4 The key to starting a chemical reaction is energy. Activation energy is the minimum amount of energy needed for reactants to form products in a chemical reaction.
5 Sometimes, the energy required for a reaction to take place is too high. The reaction can’t take place unless additional substances are present to reduce the activation energy.This substance are known as Enzyme, which serve as catalysts
6 A catalyst lowers activation energy Catalysts are substances that speed up chemical reactions- decrease activation energyEnzymes are catalystsMost reactions would occur too slowly without the help of enzymes, which speed up chemical reactions
7 Characteristics of Enzymes Enzymes are proteins2. Enzymes are reusable!3. Enzymes denature in high temperatures* denature = destroyed, broken apart, digested* denaturation is not reversibleAll enzymes end with ‘ase’.Ex) Lactase breaks down Lactose (milk sugar)
8 The lock-and-key model helps illustrate how enzymes function Enzymes are SPECIFIC (they break down only one thing)*They will only FIT with certain substrates*substrates brought togetherAttach to the active site- bonds in substrates are made or broken- product is releasedSubstrates bind to an enzyme at certain places called active sites.The enzyme brings substrates together and weakens their bonds.The catalyzed reaction forms a product that is released from the enzyme.
10 ‘Lock and Key Model’ – says there is a perfect fit between active site and substrate
11 VOCABULARYEnzymes – biological catalyst or special protein that speeds up a chemical reactionCatalyst – substance that speeds up a chemical reaction)Substrate – material that binds to the enzymeActive Site- Location on the enzyme where the substrate binds
12 Parts of Enzyme Works Reactant Enzyme-Substrate Complex Products Active siteUnchangedenzyme
14 How do enzyme speed up reactions? Enzymes lower the activation energy
15 Factors that affect Enzyme activity 1. TEMPERATURE 2. pH
16 1. What is this graph showing? temperature and enzyme activity2. What is the independent variable?temperature3. What is the optimum temperature for the enzyme?40°C4. At what temperature is the enzyme completely denatured?62°C
17 If you did not complete lab. Do that FIRST! Enzyme worksheetPg and 4Pg : 1,2,4,7,14-23