Wednesday, 9/12/12

• Finish Toothpickase Activity must be completed today!!! –Due tomorrow!!!!!

• 1st lab this week – set up today, lab Thursday & Friday – no open toed shoes!

• Chp.4,5,8 Test next Monday TUESDAY!–Carbon, Biomolecules, Enzymes

• Use small spiral notebook to set up and record labs• Use the first page to create a table

of contents• # the notebook pages

AP Bio Lab # 13Enzyme Activity

Pg. 3 – Start with Lab Title

Before doing this lab, you should understand:

• The general functions and activities of enzymes

• The relationship between the structure and function of enzymes

• The concept of initial reaction rates of enzymes

• How the concept of free energy relates to enzyme activity (view graph)

• That changes in temperature, pH, enzyme concentration, and substrate concentration can affect the initial reaction rates of enzyme-catalyzed reactions (view graph)

Under title, subtitle first section: Learning Objectives

• Students will use the catalase reaction to demonstrate different variables’ effect on enzyme activity: – such as temperature and the presence of catalase.

• Students will observe the reaction of hydrogen peroxide and catalase: – establish a baseline determining the amount of hydrogen

peroxide in a 1.5% solution,– Determine the rate of spontaneous conversion of hydrogen

peroxide to water and oxygen– determine the rate of hydrogen peroxide decomposition by

enzyme catalysis.

Next section, title: Background Info

• In this experiment, we will be using the enzyme catalase. – found inside peroxisomes in almost all organisms. – catalyses the breakdown of hydrogen peroxide to

water and oxygen. – Without this enzyme, hydrogen peroxide would

destroy our cells because it is a toxic metabolic waste product of aerobic respiration.

2 H2O2 2 H2O + O2 (gas)

Background Info Cont:

• Reaction is spontaneous (will occur naturally), but very slowly.

• If catalase is boiled, it will become denatured and will no longer function to break down hydrogen peroxide.

• The rate of this reaction will decrease as the concentration of hydrogen peroxide (the substrate) decreases.

Safety

• Read all instructions before beginning lab.• Wear personal protective eyewear (PPE) at all

times, included during clean-up.• Wear gloves and aprons, Potassium

Permanganate will stain clothes!• Be careful with chemicals, Sulfuric Acid is

highly corrosive! • Wash hands before leaving lab.

Set-up

• picture

Part A: DemoMix Hydrogen Peroxide (H2O2) + Catalase

The General Procedure

• H2SO4 stops the reaction!Measure using Potassium Permanganate Drops

Part B: Establishing a Baseline – Determining the Amount of Hydrogen Peroxide (H2O2) in a 1.5% solution

• Add Hydrogen Peroxide (H2O2)• Add Water (control)• Add Sulfuric Acid (H2SO4)

• Titrate with Potassium Permanganate (KMnO4)

• Amount of (KMnO4) used to titrate is proportional to amount of (H2O2) present in the solution

Part C: Demo Overnight

• Control Group: Do NOT add any catalase enzyme, and measure rate of Hydrogen Peroxide Spontaneous Decomposition

Part D: Rate of Hydrogen Peroxide Decomposition by Enzyme Catalysis

1. After you get your baseline

2. Add Hydrogen Peroxide (H2O2) and Catalase solution, swirl for 10 seconds

3. Add Sulfuric Acid (H2SO4) to stop reaction

4. Titrate with Potassium Permanganate (KMnO4)

5. Repeat for 30, 60, 120, & 180 seconds

1. Start Adding one drop at a time

2. Swirl, if solution turns back clear, continue adding one drop at a time

3. Stop adding drops when solution remains a pinkish – yellowish color, measure & record amount of KMnO4 used.

Next section, title: Data

• Glue in all 4 data tables –Be sure to keep the titles attached so you

know what data table is used for which section of the lab

Next section, title: Conclusion

• You will receive conclusion questions to glue in and answer in this section