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Watch the PowerPoint presentation and copy the notes.When finished, assemble in a lab group of 2 students and begin planning your experiment.A rough overview of your experiment is due at the end of class that includes:HYPOTHESISLIST OF MATERIALSPROCEDURE
BACKGROUND INFORMATIONInside the cells of a potato is an enzyme called “catalase”.This enzyme breaks downhydrogen peroxide(H2O2) and producesoxygen gasandwater.
2 H2O2(l) O2(g) + 2 H2O (l)
The more active the enzyme, the moreoxygen(and water) it produces.We can use therate of production of oxygenas a measure of enzyme activity. And we can determine the relative influence of varyingdifferent factors on enzyme activity.
Enzyme Activity
Oxygen Production
As enzyme activity increases, so does oxygen production
Since enzymes are proteins, enzyme activity is affected by changes inpH(measure of acidity).If the pH changes are too drastic, enzymes can becomedenaturedand their activity is reduced or abolished.
Oxygen Production
pH A
pH is affecting enzyme activity so that oxygen production is decreased
pH B
pH C
(as a measure of enzyme activity)
Enzyme activity may also be adversely affected by changes intemperature.Normally, enzymes work at a particulartemperature optimumand if the temperature is either too high or too low, the enzyme activity is reduced.
Oxygen Production
Temp 1
Temperature is affecting enzyme activity so that oxygen production is decreased
Temp 2
Temp 3
Enzyme activity can also be affected bysurface area, ie. the more enzyme exposed to substrate or the more substrate exposed to enzyme.For example, if potato cells are crushed or cut into smaller pieces, this may affect how much catalase enzyme comes into contact with substrate (H2O2).
Potato pieces
Oxygen bubbles
The more bubbles, the more oxygen. Therefore, the more active the enzyme.
THE EXPERIMENTYou and your lab partner will design an experimental procedure based on what you would like to study.Decide whatindependent variable(ie. pH, temperature, surface area, etc.) you want to manipulate to determine its effect on enzyme activity.Yourdependent variableis the rate or amount of oxygen production and you will need a number ofcontrolled variables.
Use3 different changesto your independent variable (ie. neutral pH, acidic pH, basic pH).Consider thematerialsyou will need to perform the experiment. You will have access to standard laboratory equipment including:Potatoes, scalpels, forcepsHydrogen peroxide solutionAcid, base, waterHot plate, thermometerBeakers, test tubes, graduated cylinders, droppers, retort stand, clampA few other select items may be available
Only typical lab equipment available. Any additional materials must be provided by student.
LAB FORMATHypothesis:Create an IF / THEN statement about your experiment.Materials: List of items.Procedure:Past tense, impersonal, numbered steps which describes experiment and includes all materials used.Observations:Record data on oxygen production in a well-designed and titleddata table.Present data in a well-designed and titled computer-generatedgraph.
Conclusions:Describe your independent, dependent and controlled variables.Explain how changing your independent variable influenced the enzyme activity and explain why.List and explain at least three possible experimental sources of error in this lab activity.
NOW DO THISAssemble in a lab group of 2 students and work on designing your experiment. Consider what your variables will be and what materials you need to conduct the experiment.You will only have access to typical lab materials. Feel free to look around the room on shelves and lab drawers to determine some of the items available.Submit at end of class with your names:-Hypothesis, Materials, Procedure





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