Enzymes: Form and Function
Lower activation energy of reaction
Combine or break apart substrates
Not used up in reaction
End in –ase
Lactase metabolizes lactose
DNA Polymerase – polymerize nucleotides
Substrate to product
Energy of activation with enzyme
Energy needed to run reaction without an enzyme
Temp & pH
Changes in environmental conditions will alter enzyme structure, and therefore alter its function
Enzyme activity measured by
Initial reaction velocity (IRV)
Amount of product per time
this is what you’re doing in today’s experiment
Or could use amount of product per degree (for a temperature graph)
what is shown in the graph above
IRV = (slope of the graph)
Reaction you will run:
the reaction goes from clear to brown
peroxidase is not used up in reaction
guaiacol gets oxidized; hydrogen peroxide gets reduced
This is a redox reaction; Think about how rust turns a different color when iron is oxidized
Baseline: Filtered water – are the enzyme concentrations too weak/strong?
Question: how does pH impact the function of peroxidase?
Experiment: try at pH of 4, 7, and 10
guaiacol (clear) + H2O2 tetraguaiacol (brown) + H20
USE CORRECT PIPETTE FOR EACH CHEMICAL
Make sure to only take out 300 microliters of Guaiacol
100 microliters to .1 milliliter
Get Guaiacol from me
Prepare your blank to tare the colorimeter – fill cuvette 2/3 full and make sure the clear side of cuvette is perpendicular to the colorimeter’s light
Don’t touch the clear sides (fingerprints are a problem).
Don’t turn upside down. 1st resistance to extract chemical; 2nd resistance to eject chemical. Pay attention to units on pipette. Don’t reuse tips.
Before adding enzyme solution to test, have all of your supplies ready:
your colorimeter tared and ready to go
Guaiacol, pH buffer, and H202 in a test tube
Once enzyme is added, quickly pour into cuvette and place in colorimeter, recording every 15 sec.
Input data into excel sheet for all of class to record
Calculate IRV using greatest difference between two adjacent points
You will make a line graph of our data using Excel (there will be 4 lines on graph)
BRING THIS GRAPH NEXT WEEK TO CHECK CORRECTNESS!
We will cover components of the lab report following your lab practical next week
You will have access to sample lab reports, rubrics, instructions
Topic: Effects of pH on Peroxidase