Catalysts Reduces the amount of activation energy needed for a reaction to take place.

A type of catalyst. A type of catalyst. A protein that speeds up a metabolic reaction by lowering the activation energy needed. A protein that speeds up a metabolic reaction by lowering the activation energy needed. Name usually ends in “-ase” and also indicates the substrate it acts on. (ex: Lipase (breaks down…?) Name usually ends in “-ase” and also indicates the substrate it acts on. (ex: Lipase (breaks down…?) Very small amounts needed Very small amounts needed  Reusable (are not changed or destroyed)  Highly specific (ex: catalase only works on Hydrogen peroxide) (ex: catalase only works on Hydrogen peroxide)

Examples: Digestive Enzymes Digestive enzymes are secreted along the digestive tract. Allow the nutrients in food to be broken down and absorbed into the blood stream. Most produced by the pancreas. Human digestive enzymes include ptyalin, pepsin, trypsin, lipase, protease, and amylase.

Lactose intolerance The inability to metabolize lactose, a sugar found in milk and other dairy products. The required enzyme lactase is absent in the intestinal system. Symptoms of lactose intolerance include loose stools, abdominal bloating and pain, flatulence, and nausea.

Enzymes are affected by temperature, pH, concentration *Can be denatured (change shape & lose function) saturation point.

Activation energy energy required to start a reaction. (with and without an enzyme)

Substrate & Active site The substrate is the substance that the enzyme is working on. Active site – Where the enzyme attaches to the substrate.

Lock & Key Model

Competitive Inhibitor Molecule competes for the “active site” Molecule competes for the “active site”

Noncompetitive inhibitor If the enzyme is an allosteric enzyme, the presence of a noncompetitive inhibitor changes the shape of the enzyme and prevents the reaction from occurring. If the enzyme is an allosteric enzyme, the presence of a noncompetitive inhibitor changes the shape of the enzyme and prevents the reaction from occurring.

Practice 1. What is the area of an enzyme called where the chemical reactions occur? a. The Cytoplasm b. The Active Site c. The Catalyst d. The Nucleus

Practice 2. What is the name of the enzyme that helps to break down pectin in fruit to release more of their juice? a. Protease b. Amylase c. Glucose d. Pectinase

Practice 3. Enzymes accelerate reactions by ___ the activation energy needed for the reaction. a. stopping b. raising c. lowering d. binding

Practice 4. What happens to an enzyme when it denatures? a. The activation energy of the reaction is doubled. b. The activation energy of the reaction is lowered. c. It's optimal conditions for temperature of the enzyme are doubled. d. The shape of the enzyme molecule is changed.

Practice 5. Which statement best describes the enzyme represented in the graphs above? a. This enzyme works best at a temperature of 35 C and a pH of 8. b. This enzyme works best at a temperature of 50 C and a pH of 12. c. Temperature and pH have no influence on the activity of this enzyme. d. This enzyme works best at a temperature above 50 C and a pH above 12

Practice 6. A competitive inhibitor of an enzyme is usually: a. a highly reactive compound. b. binds at a site other than the active site. c. structurally similar to the substrate. d. water insoluble.