6.2 Enzymes and Chemical Reactions pages 156-160

Chemical reactions take place all the time. Chemical reactions change substances into different ones by breaking and forming chemical bonds.

6CO2 +6H2O+light energyC6H12O6 + 6O2 Reactants are the starting materials. The newly formed substances are called products, which are different from the reactants. Reactants on the left, Products on right. For example: 6CO2 +6H2O+light energyC6H12O6 + 6O2 Products Reactants

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.

Enzymes in Chemical Reactions 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. These substance are known as enzymes, which serve as catalysts.

A catalyst lowers activation energy Catalysts are substances that speed up chemical reactions by decreasing activation energy. Enzymes are catalysts Most reactions would occur too slowly without the help of enzymes, which speed up chemical reactions.

Characteristics of Enzymes Enzymes are proteins 2. Enzymes are reusable! 3. Enzymes denature in high temperatures * denature = destroyed, broken apart, digested * denaturation is not reversible All enzymes end with ‘ase’. Ex) Lactase breaks down Lactose (milk sugar)

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 are brought together. They attach to the active site of enzymes. - Bonds are then made or broken. - Product is released. Substrates 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.

‘Lock and Key Model’ – says there is a perfect fit between active site and substrate

VOCABULARY Enzymes – biological catalysts or special proteins that speed up chemical reactions Catalysts – substances that speed up chemical reactions) Substrates – materials that bind to the enzyme Active Site - Location on the enzyme where the substrate binds

An Enzyme at Work Reactant Enzyme-Substrate Complex Products Substrate Active site Unchanged enzyme

How an enzyme affects a chemical reation:

How do enzymes speed up reactions? Enzymes lower the activation energy of a reaction:

Factors that Affect Enzyme Activity TEMPERATURE Too warm, enzyme will denature. Too cold, enzymatic activity will slow down. 2. pH - a change in pH can change the shape of the enzyme so that substrates can’t fit into active site.

1. What is this graph showing? temperature and enzyme activity 2. What is the independent variable? temperature 3. What is the optimum temperature for the enzyme? 40°C 4. At what temperature is the enzyme completely denatured? 62°C

If you did not complete lab. Do that FIRST! Enzyme worksheet Pg 160 1 and 4 Pg 175-176: 1,2,4,7,14-23