ap biology - r. wingerden lab: •complete labbench activity lab 2: enzyme catalysis in your comp...

Pearson Education, Inc., publishing as Person Benjamin Cummings College Board, AP Biology Curriculum Framework 2012-2013

Copyright © Rebecca Rehder Wingerden

Investigation 13: Enzyme Activity

AP Biology Investigation 13: Enzyme Activity

Learning Objectives • To understand the relationship between enzyme

structure and function.

• To make some generalization about enzymes by studying just one enzyme in particular.

• To determine which factors can change the rate of an enzyme reaction.

• To determine which factors that affect enzyme activity could be biologically important

Copyright © 2012 Rebecca Rehder Wingerden

Background • Enzymes are the catalysts of biological systems. They

speed up chemical reaction in biological system by lowering the activation energy, the energy needed for molecules to begin reacting with each other.


The energies of the stages of a chemical reaction. substrates need a lot of potential energy to reach a transition state, which then decays into products.The enzyme stabilizes the transition state, reducing the energy needed to form products.


Background • Enzyme form an enzyme-substrate complex that

reduces energy required for the specific reaction to occur.

• Enzyme have specific shapes and structure that determine their functions.



Background • Enzymes are fundamental to the survival of any living

system and are organized into a number of groups depending their specific activities.


- Catabolic enzymes - break down: • proteases breaks down proteins • lactase breaks down milk sugars

- Anabolic enzymes - to build: • ATP Synthase the enzyme that

stores cellular energy in ATP by combining ADP and phosphate

• Rubisco the enzyme involved in the building of sugar molecules in the Calvin cycle of photosynthesis ATP Synthase a vital enzyme used

in oxidative phosphorylation


Background • Catalase is a common enzyme found in nearly all living

organisms exposed to oxygen. It catalyzes the decomposition of hydrogen peroxide to water and oxygen.


2 H2O2 2 H2O + O2catalase

hydrogen peroxide

water oxygen

Catalase enzyme can catalyze the decomposition of hydrogen peroxide, converting millions of molecules of hydrogen peroxide to water and oxygen a second.

In this lab you will use the floating disc method to observe the action of the enzyme catalase on its substrate, hydrogen peroxide.

Once a baseline reaction rate is determine you will design an experiment to test how abiotic or biotic factors influence the rates of enzymatic reactions.


Complete the following before conducting this investigation:

I. Read Investigation 13: Enzyme Activity. II. Answer the following PreLab questions in your

Comp Book: 1. Summarize what you will be doing in this

investigation. 2. What is the primary question you will be trying to

answer in this investigation?


PreLab


Pre Lab: • Complete LabBench Activity Lab 2: Enzyme Catalysis

in your Comp Book

- http://www.phschool.com/science/biology_place/labbench/lab2/intro.html (handout)

• View BozemanScience.com: AP Biology Lab 2 Enzyme Catalysis (Float Disc Method)

- http://www.bozemanscience.com/ap-bio-lab-3-enzyme-catalysis



BozemanScience.com: AP Biology Lab 2 - Enzyme Catalysis (7:00 min.) http://www.bozemanscience.com/ap-bio-lab-3-enzyme-catalysis


Designing and Conducting Your Investigation: Yeast Catalase Experiment • Read Yeast Catalase Experiment (handout) • Copy Table 1: Catalase Reaction Rate Baseline

RXN (GROUP) • Copy Table 2: Catalase Reaction Rate Baseline

RXN (CLASS) • Complete Yeast Catalase Experiment - Part 1:

Baseline Activity for the standard yeast solution and 3% hydrogen peroxide.


Designing and Conducting Your Investigation: Yeast Catalase ExperimentTable 1: Catalase Reaction Rate Baseline RXN (GROUP)


Group Group Average Float Rate

1

2

3

4

5

6

Class Average

Table 2: Catalase Reaction Rate Baseline RXN (CLASS)

Trial Float Time (sec.)

Rate (1/sec)

1

2

3

4

Group Average


Part II: Independent Experiment • Purpose: method that will be used, independent

and dependent variable. • Hypothesis: If (rational for the investigation), then

(outcome that you would expect). • Procedure: Steps discussing how you will modify

the procedure: independent (levels), dependent, control, and standardized variables.

• Data: table(s) to record findings • Approval by Instructor



Designing and Conducting Your Investigation: Yeast Catalase Experiment


Float Time (sec.)

Trial No Catalase (control)

Baseline Catalase x0.5

Baseline Catalase x2.0

1

2

3

4

Average

Table 3: Catalase Concentration Reaction Rate Experimental



Designing and Conducting Your Investigation: • Analyze your results by graphing the data collected.

- Remember in order to express the rate as a number with a direct relationship to the rate, take the number (or average number) of seconds it took the disc to float and invert it.

- For example, if it took 5.48 seconds, the rate would be expressed as 1/5.48, which equals 0.18 (round to hundredths).


Whiteboard Presentation: • Purpose: method that will be used, independent and dependent variable.

• Hypothesis: If (rational for the investigation), then (outcome that you would expect).

• Procedure: Steps discussing how you modified the Floating Disk procedure. Discuss the different levels of the independent variable in your design.

• Analysis: - Graph: Catalase Reaction Rate …your variable…

• Summary Statement: Describe: HOW your IV influences the DV. Compare your experimental data to the baseline rate. Explain: WHY did your IV effect/not effect the baseline rate.




Designing and Conducting Your Investigation: • Conclusion:

- restate the purpose of this experiment - restate your hypothesis for this experiment - statement: do the results of your experiment support or

refute your hypothesis - list and explain the data that lead you to your

statement - list and explain statistical test(s) to support statement - Therefore, conclusion (remember experimental

purpose) • Post Lab complete questions 1-7 on the next slides on

on lab handout. Copyright © 2012 Rebecca Rehder Wingerden


Post Lab Questions (1-7) 1. What is the function of enzymes in a living system? 2. Different enzymes work better under different conditions.

Where in a human body might it be beneficial to have enzymes that work well in very acidic environment? Explain your answer.

3. There is a large amount of catalase found in a human liver. Would the liver break down more hydrogen peroxide in the summer or winter? Explain your answer.

4. Of the thousands of enzymes known, there is a family of enzymes called proteases that catalyze a reaction which breaks down proteins. What do you think would happen if you added a protease to your sample of catalase before proceeding with your experiment? Explain why you came to this conclusion.



Post Lab Questions (1-7) 5. Copy the graph show in Figure 1 to your paper. Using

different colors, draw how you would expect the reaction rate to change if the substrate (H2O2) concentration was increased and if it were decreased.

Key • baseline

reaction rate

• increase in substrate

• decrease in substrate

Catalase Reaction

Oxy

gen

Prod

uced

(mm

)

0

10

20

30

40

50

60

Time (minutes)

0 1 2 3 4 5 6 7 8 9 10Figure 1



Post Lab Questions (1-7) 6. Explain what is going

on in Figure 2. Why does the reaction rate make a bell-shaped curve? Figure 2

7. Explain what is going on in Figure 3. Why are there three different bell-shaped curves on this graph?

Figure 3

Enzyme X Reaction Rate

Enzyme X Reaction Rate

Enzyme X, Y and Z Reaction Rate


ap biology - r. wingerden lab: •complete labbench activity lab 2: enzyme catalysis in your comp...

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