Transcript AP Bio Lab # 13 Enzyme Activity

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
Pg. 3 – Start with Lab Title
AP Bio Lab # 13
Enzyme Activity
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: Demo
Mix 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
2. Swirl, if
solution turns
back clear,
continue
adding one
drop at a time
1. Start 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