2. LAB 2 Enzyme Catalysis

3. H2O2 HYDROGEN PEROXIDE 2 H2O2 → 2 H2O + O2 In aerobic organisms
Toxic byproduct of metabolism
Strong oxidizer
(grabs electrons from other molecules)
2 H2O2 → 2 H2O + O2
Substrate Products
Reaction happens spontaneously (slowly)

4. Catalase ENZYME Speeds up reaction to break down hydrogen peroxide
Tetramer (4 polypeptide subunits)
Contains Porphyrin groups with iron cofactors = HEME
ANTI-OXIDANT

5. Other molecules with porphyrin rings
Hemoglobin
Chlorophyll

6. 2A Watch for bubbles Repeat with boiled enzyme
Repeat with diced potato

7. 2B DETERMINE BASELINE AMOUNT of H2O2 +10 mL H2O2 +1 mL H2O
+10 mL H2SO4
REMOVE A 5 mL SAMPLE
Assay for Hydrogen Peroxide

8. ASSAY for presence of H2O2
5 H2O2 + 2 KMnO H2SO4 → K2SO4 + 2 MnSO H2O + 5 O2
Potassium permanganate (KMnO4 ) = Purple
Add KMnO4 until solution stays a faint pink or brown
Syringe
Numbers run backwards
BURET

9. Enzyme Catalyzed Rate of H2O2 Decomposition
30 sec
60 sec
90 sec
120 sec
180 sec
360 sec
Redo Baseline
10 sec
+ 10 mL H2O2 to each beaker
For each time point + 1 mL Catalase (yeast) Swirl gently At appropriate time: add sulfuric acid( H2SO4 )
Assay for H2O2

11. µmoles H2O2 used
TIME (seconds)