4. Birds & Aging Many birds appear not to show the effects of cellular senescence (i.e. cells stop reproducing) This failure to show the physical effects of aging may be due to high levels of peroxidases

5. Peroxides Highly reactive, strong oxidizers When broken down slowly, may produce FREE RADICALS, which can damage DNA and other cellular structures While some free radicals may help the immune system, others may lead to oxidative stress

6. Peroxidases Enzymes that reduce the activation energy required to cause the decomposition of peroxides Rapid breakdown = fewer free radicals

7. Catalase Found in most forms of life on Earth One molecule of catalase can convert 40 million hydrogen peroxide molecules/sec 500 amino acid long protein, containing four heme (iron) rings held together in the quaternary structure Iron in heme rings reacts to pull electrons away from H 2 O 2 bonds, causing it to disassociate

8. LAB: Decomposition of Hydrogen Peroxide via Catalase Purpose: To assess the effects of enzyme concentration, ambient temperature and pH on the rate of decomposition of hydrogen peroxide Method: Measure rate of pressure change (kPa/sec)

9. Concentration and Reaction Rate Because the relationship between substrate and enzyme is so specific, changing the number of enzymes reacting with the substrate (or vice versa) may affect the rate of reaction Ex: Vmax

10. Temperature and Reaction Rate Temperature is a measurement of molecular speed At a lower temperature, molecules collide less frequently At higher temperatures molecules collide more frequently Enzymes tend to have an optimal temperature at which they function

11. pH and Reaction Rate Enzymes have specific pH ranges in which they tend to function most effectively Outside of this range, enzymes can denature, causing them not to fit with their substrates If enzyme does not fit, E A is too large for the reaction to occur

12. GROUPS & VARIABLES GROUPS 1 & 4 – Concentration GROUPS 2 & 5 – Temperature GROUPS 3 & 6 – pH Dependent Variable For All = slope (m) for plot of pressure v. time

13. Lab Notes Take 20 mL of catalase suspension to your table in beaker. Use different seral pipettes to dispense H 2 O 2 and catalase suspensions Total volume in test tubes will be 7mL pH ranges tested will be 3,5,9 & 11. Change data tables to reflect this alteration. Post and average the class data

14. Part 1 Protocol Clean and dry the large test tubes If you are doing part 1 (concentration) add (in this order… – 3mL water – 1 to 4 mL of Catalase enzyme suspension – 3mL H 2 O 2 Immediately cap the tube and collect the data

15. Part 2 Protocol Clean and dry the large test tubes Place test tube into 0-5°C ice bath Add (in this order)… – 3mL water – 1 mL of Catalase enzyme suspension – 3mL H 2 O 2 Immediately cap the tube and collect the data Repeat steps at room temperature, 30-35 °C and 50-55°C

16. Part 3 Protocol Clean and dry the large test tubes Add (in this order)… – 3mL pH 3 solution – 1 mL of Catalase enzyme suspension – 3mL H 2 O 2 Immediately cap the tube and collect the data Repeat steps using 3mL of pH 5, 9 and 11