Birds & Aging Many birds appear not to show the effects of cellular senescence (i.e. cells stop...
-
Upload
daisy-gordon -
Category
Documents
-
view
218 -
download
0
Transcript of Birds & Aging Many birds appear not to show the effects of cellular senescence (i.e. cells stop...
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
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
Peroxidases
• Enzymes that reduce the activation energy required to cause the decomposition of peroxides
• Rapid breakdown = fewer free radicals
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 H2O2 bonds, causing it to disassociate
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)
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
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
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, EA is too large for the reaction to occur
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
Lab Notes• Take 20 mL of catalase
suspension to your table in beaker.
• Use different seral pipettes to dispense H2O2 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
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 H2O2
Immediately cap the tube and collect the data
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 H2O2
Immediately cap the tube and collect the dataRepeat steps at room temperature, 30-35 °C and 50-55°C
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 H2O2
Immediately cap the tube and collect the dataRepeat steps using 3mL of pH 5, 9 and 11