The Effect of Temperature and pH on Enzyme Activity

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Title: The Effect of Temperature and pH on Enzyme Activity

OBJECTIVE/INTRODUCTION

The purpose of our lab was to observe how the reaction rate of an enzyme increases or decreases when combined with different substrates. Enzymes are catalysts that increase the rate of biochemical reactions. The rate of these reactions can be affected by its environment: temperature and pH. Low temperatures can cause enzyme reaction rate to become inactive or very slow by causing less collision of molecules and high temperatures can cause enzymes to denature prompting the reaction rate to lessen. As temperature increases, the rate of an enzyme-catalyzed reaction should increase. Similarly, the pH of an environment can affect the shape of an enzyme decreasing or increasing its reaction. In addition, all enzymes have a different optimal pH. As pH increases, the rate of an enzyme-catalyzed reaction should increase. In this lab, to examine the effects of temperature and pH on the reaction rate of an enzyme, we utilized potato extract (catecholase) as our enzyme combined with the substrate catechol. We utilized the Spec 20 to determine the reaction rate of enzymes under different conditions because once the enzyme and substrate are combined in the test tube the reaction begins to occur forming benzoquinone. The product benzoquinone is a brown color and the darker the color the less light will be able to pass through the test tube causing the percentage of light absorbed to increase. The absorption of light will be measured by the Spec 20 allowing us to observe the enzymes reaction rate.

MATERIALS/METHOD

Spectrometer

Pipette

Catechol

Potato Extract

Glass Tubes

This lab was a two-part lab where we analyzed the rate of enzyme reactions at different temperatures and later we looked at how pH levels are affected by enzyme-catalyzed reactions. To test the effects of temperature on enzymatic reactions, we filled 5 test tubes with 4 mL of water and 1 mL of potato extract. Then we filled another tube, which we referred to as the blank, with 1 mL of potato extract and 6ml of water (the extra 2 mL of water is added to offset the 2mL of catecholase that will be added later). From here we put all the tubes except the blank, which served as the control of the experiment, into different temperature environments. The temperatures used were 0℃, 18 ℃, 30 ℃, 40 ℃, and 60 ℃. We left the tubes in these conditions for 5 minutes before adding catechol to the tubes then we reinserted the tubes back in these temperature controlled environments for another 5 minutes. The next step after this was to test light absorbance through the use of the Photospectrometer (Spec 20). The higher the absorbance value determined the rate of the chemical reaction. For the section portion of the lab, we tried to see how pH balance affects enzymatic reaction rates. We filled the 5 tubes with 1 mL of potato extract and 4 mL of pH buffer solution. Each tube had varying pH buffer levels. The levels were pH levels of 3, 5, 7, 9, 11 and of course the blank which is our control tube was filled with 1 mL of potato extract and 4 mL of pH 7 buffer which is neutral. We then used parafilm and inverted to mix each solution and added 2 mL of catechol to all 5 test tubes. We waited 5 minutes for the chemical reaction to take place before calibrating the Spec 20 to test the absorbance.

RESULTS

Table 1: Effect of Temperature on Enzyme Reaction Rate

Sample

Temp (℃)

Absorbance after (5 minutes)

1

0℃

.167

2

18℃

.179

3

30℃

.202

4

40℃

.211

5

60℃

.112

Graph 1: Effect of Temperature on Enzyme Reaction Rate

Table 2: Effect of pH on Enzyme Reaction Rate

Sample

pH

Absorbance after (5 minutes)

1

3

.107

2

5

.121

3

7

.197

4

9

.007

5

11

.010

Graph 2: Effect of pH on Enzyme Reaction Rate

As seen in table and graph 1, the effect of temperature on enzyme reaction rate, as the temperature increased the absorbance also increased until it peaked at sample 4 with a temperature of 40℃ which had an absorbance of .211. In the last sample, sample 5 with a temperature of 60℃, the absorbance began to decrease with an absorbance of .112. In table and graph 2, the effect of pH on enzyme reaction rate, the highly acidic samples (1 and 2) had greater absorbance than the basic samples (4 and 5) which had the lowest absorbance out of all the samples. The highest absorbance was in sample 3 (absorbance of .197) which had a neutral pH of 7.

DISCUSSION (need to be done)

Directions: This section should not just be a restatement of the results but should emphasize interpretation of the data, relating them to existing theory and knowledge. Suggestions for the improvement of techniques or experimental design may also be included here. In writing this section, you should explain the logic that allows you to accept or reject your original hypotheses. Provide a conclusion based on the results that you got.

example: My hypothesis was clearly false, as some ions or cofactors had more rates of absorbency than others. This data suggested that copper is the most crucial to the enzymatic reaction as it had the lowest absorbency when bound to prevent reaction. Cofactors such as copper, calcium, and magnesium were tested by using chelating agents to bind them to prevent them from catalyzing them enzymatic reaction. As a result, their efficiency entirely depended on low absorbance rate. Since Tube 4 was the control, we would have thought that it would have the highest absorbance rate as the enzymatic reaction there were no chelating agents binding it.This may have been a possible error such as miscalculation on the portion of the mixture such as having lest EDTA chelating agents, that Tube 1 had fingerprints.There may also be possible errors such as

inaccurate timing mixing the catechol into the solution or the water bath. If this is not the case, we would suspect that there are cofactors of the enzyme that could actually slow down the enzymatic reaction rather than speeds it up. The rate of absorbance was calculated by subtracting the absorbency at 20 minutes to the absorbency at 10 minutes. I concluded this experiment may have possible errors, but suggests that copper bound by Citric acid is the most effective for the

enzymatic reaction of benzoquinone.

 
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Case Study

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“Can Suminoe Oysters Save Chesapeake Bay?” by Nieman & Liu Page 

Annapolis, January 2008 “If you don’t do the right thing, we will take matters into our own hands.”

State Senator Ben Fisher hung up the phone slowly. ” at was one of his constituents, one of the many he had heard from that day, each one angrier than the last it seemed. His was the swing vote on the Assembly bill funding the full-scale introduction of sterile Suminoe oysters to the Maryland side of the Chesapeake Bay. ” e bill was an attempt to try to off -set the eff ects of declining populations of native oysters in the bay, the result of habitat degradation, over-harvesting, and disease. Introducing the Suminoe oysters would be an expensive and risky undertaking, but there were costs—both environmental and economic—of doing nothing, too.

Environmentalists were divided, “clean” versus “pristine.” Some demanded widespread seeding of the imported oysters to deal with worsening water quality that was wiping out aquatic life in the bay. Others warned that this could be a bigger disaster than kudzu. Test introductions in Virginia had been limited and closely monitored—and so far so good. But scientists warned that a few oysters would be fertile and might proliferate, forcing out the last of the Eastern oysters or interbreeding with the native species – bringing who knew what changes to the already damaged ecosystem?

Ben gazed out his offi ce window. “CLEAR THE BAY!” said one of the banners that blocked his view of the sailboats in the harbor. “DON’T TINKER WITH A NATIONAL TREASURE!” warned another.

Business interests held all sorts of positions. “We’d rather see those tax dollars go into developing infrastructure for high-end development,” a major developer with plans for summer homes, condos and retail shops had emailed Ben. “Do you know what that land is worth under those broken-down, abandoned fi shing shacks?” He didn’t need to add that he put a lot of money into political campaigns.

” e owner of a fi sh market had called earlier in the day, worried that the oysters, whether native or otherwise, might not be fi t for eating as a result of all the pollution they fi ltered from the water. She had few oysters to sell now—would the new ones appeal to customers?

” e Delmarva Peninsula poultry producers didn’t want any more controls on the nutrient load entering the bay. ” ey felt there were too many controls as it was, and warned that more controls would hamper their operations. ” ey were all in favor of the oysters as a solution. So were the charter-boat owners who wanted clear water for the rockfi sh.

The commercial fishing industry wanted the oysters too, and now. Boats were idled and processing plants were handling trucked-in Louisiana oysters. The biggest plant in Ben’s district said it would close this year if things didn’t change. These new oysters grew three times as fast, they said. It wasn’t too late to save an industry.

Can Suminoe Oysters Save Chesapeake Bay? by Valerie Nieman Department of English Department of Journalism and Mass Communication North Carolina A&T State University Zhi-Jun Liu Department of Geography University of North Carolina—Greensboro

 

 

“Can Suminoe Oysters Save Chesapeake Bay?” by Nieman & Liu Page 

Image Credit: Copyright © Robert Kyllo. Copyright ©  by the National Center for Case Study Teaching in Science. Originally published // at http://www.sciencecases.org/chesapeake_bay/chesapeake_bay.asp Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

On the other hand, the State of North Carolina was threatening a lawsuit, fearful that the nonnative oysters would spread down the coast and aff ect their beds. ” ey cited the destructive virus brought in by oyster introductions decades ago.

And many of Ben’s constituents were in an uproar over the expense that Marylanders would bear for the oyster option—or the alternative. Towns and cities didn’t want to spend money to upgrade their sewer systems when so much pollution came from out-of-state.

Even within the Senator’s own family there was division. His father, who had started tonging oysters when he was a boy, said it was time to let the old ways go, that fi shing was no way to make a living these days. Spend the money elsewhere. His daughter, a member of a cultural preservation group, pleaded: “We need to preserve the watermen culture. We need the oysters.”

And now this dramatic phone call—desperate people threatening to take the matter into their own hands and dump imported oysters—nonsterile ones that could reproduce and spread—into the bay to restore the beds. ” e debate had dragged on too long, they said. A decision had to be made.

Senator Ben Fisher left his offi ce and walked down the echoing hall to the Assembly chamber, where he would have to cast his vote.

Questions . Who is being aff ected by this decision and how? . If the decision is made to introduce the Suminoe oysters, what might be the long-term eff ects on

the environment, the communities, the people? . Any choice implies other lost opportunities. In what alternative ways might this money be spent

to deal with the Chesapeake Bay’s problems and serve constituents? . What might this region look like in  years if nothing is done? . What should Senator Ben Fisher do?

 

 
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Biology Forum Post

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This week we continue to look at a case study about Dr. E.L. Trudeau, who performed a seminal early experiment validating the germ theory of infection. Part II of our discussion places the findings of Trudeau’s Rabbit Island experiment in a broader social context

Read through (make sure you include the question Answer any 3 questions the attached case study. numers) and write your post in a narrative format based on your answers to the questions.

Post must be 250 words.

I have attached Part 2 of the case study that has the questions to answer. Only chose 3 out of the 4 questions to answer, not all need to be answered.

NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE

Page 5“A Simple Plan” by Karen M. Aguirre

Part II – Tuberculosis in Social Context E.L. Trudeau was quick to distinguish between a helpful therapy and a cure. He opened the Adirondack Cottage Sanitarium, where poor and rich alike could come and receive the bene” ts of fresh air, plenty of sunlight, rest, and abundant but simple nourishing food. Hundreds bene” ted. Similar institutions opened up in the U.S., and the movement was already well underway in Western Europe. But the cure would only come in the 1950s with the discovery of antibiotics that were e# ective against the mycobacterium.

Question 1: $ e curve shown in Figure 2 has three parts, from 1700–1800, 1800 to approx. 1955, and 1955 to approximately 1985. $ e data used to produce the curve are from Western Europe, but a similar one could be expected for the United States. From what you know of the history and culture of the United States and Western Europe, write a sentence telling why each part of the curve looks the way it does. In looking just at this graph, what would you predict about the death rate from TB in 2000 and 2005?

In recent years, a combination of development of antibiotic resistant strains of MTb along with the creation of a reservoir of immunocompromised people by the worldwide AIDS epidemic have contributed to a resurgence of tuberculosis in the United States and a worldwide upswing in TB cases and deaths. $ is resurgence has been accompanied by a resurgence of interest in the disease by scientists asking new questions about the nature of true host genetic susceptibility/resistance genes for tuberculosis, about virulence genes within the mycobacterium itself which might o# er new drug targets, and about the epigenetic factors that may in% uence disease predisposition and outcome in people with tuberculosis.

Question 2: Tuberculosis causes nearly 2 million deaths worldwide each year. Between 1985 and 1992, cases of TB in the United States increased by 20 percent, as shown in Figure 3. Write a paragraph suggesting a few reasons why this resurgence of TB might have occurred in the United States.

Question 3: $ e resurgence lasted until approximately 1992, then, in the United States, it began to abate. In 2005 the TB case rate in the U.S. was 4.8 per 100,000, as the U.S. medical community brought the epidemic under control (Centers for Disease Control & Prevention, National Prevention Information Network, n.d.). However, in U.S. prisons and all over the world TB remains a serious health problem. In the U.S., zero tolerance drug laws have resulted in a burgeoning incarcerated population, which constitutes a signi” cant reservoir of disease, with a far higher incidence rate than the general population. In New York prisons, the incidence rate of TB is 156.0/100,000compared to the rate of 10.4/100,000 in the general population (U.S. Agency for International Development, 2009). Considering all you have learned in Parts I and II, discuss why these rates may be so much higher in prison.

Figure 3: TB Cases in the United States

Figure 2: Western European mortality statistics—TB deaths over time (Based on Murray, 2001).

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NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE

Page 6“A Simple Plan” by Karen M. Aguirre

‱

Photo in title block © Paul Lemke | Dreamstime.com, id#18581133. Case copyright held by the National Center for Case Study Teaching in Science, University at Bu# alo, State University of New York. Originally published December 18, 2012. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

In 2006, there were 9 million new cases of tuberculosis worldwide, many of these caused by drug-resistant strains of the mycobacterium. Scientists struggle to ” nd new drugs that will be e# ective against the resistant strains and to propose better treatment regimens involving more direct observation of treatment (DOT) to assure patient compliance. Additionally, many have called for public acceptance and physician support for more responsible dispensing of antibiotics. $ ese are di0 cult and complex problems that require a resolve on the part of many sectors coupled with a willingness to devote adequate resources to a ” ght a disease that most often strikes people in the poorest of places.

Additionally, it is certainly the case that many modern TB cases occur in a global incarcerated population of approximately 8 million (U.S. Agency for International Development, 2009). Many of those incarcerated were political prisoners taken prisoner in war zones. Conditions in the prisons include inadequate ventilation, poor nutrition, negligent healthcare, HIV co-infection, and rampant despair. How does this resonate with what you’ve learned of E.L. Trudeau’s experience in the late 19th century?

We know a lot about how to prevent and treat tuberculosis. $ ere is much more to be learned. In 2010, 8.8 million people in the world fell ill with TB and 1.4 million died (World Health organization, 2012).

Question 4: All of the following factors are important in causing the worldwide resurgence of tuberculosis: (a) emergence of strains that are resistant to one or more of the available antibiotics e# ective against MTb; (b) incomplete or inadequate understanding by scientists of the details of the host/pathogen interaction in MTb infection; (c) lack of a universally-accepted vaccine; (d) lack of ” nancial support for science and for public health initiatives in developing countries; (e) famine; (f ) geopolitical instability in the developing world; and (g) inadequate public awareness of public health issues. If you were a billionaire philanthropist like Warren Bu# et or Bill Gates, where would you focus your e# orts against tuberculosis?

References Centers for Disease Control & Prevention (CDC), National Prevention Information Network. ! e Changing

Epidemiology of TB. http://www.cdcnpin.org/scripts/tb/tb.asp Last accessed: 10/12/12. Murray, J.F. 2001. A $ ousand Years of Pulmonary Medicine: Good News and Bad. European Respiratory Journal

17(3): 558–565. U.S. Agency for International Development (USAID). 2009. Guidelines for Control of Tuberculosis in Prisons. http://

pdf.usaid.gov/pdf_docs/PNADP462.pdf Last accessed: 10/12/12. Who Health Organization. 2012. Tuberculosis Fact Sheet. http://www.who.int/mediacentre/factsheets/fs104/en/ Last

accessed: 10/12/12.

 
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Biology Lab

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Lab 2 Cell Structure and Function BIO101L

 

 

Student Name: Click here to enter text.

Access Code (located on the lid of your lab kit): Click here to enter text.

Pre-Lab Questions

1. Identify three major similarities and differences between prokaryotic and eukaryotic cells.

Click here to enter text.

 

2. Where is the DNA housed in a prokaryotic cell? Where is it housed in a eukaryotic cell?

 

 

3. Identify three structures which provide support and protection in a eukaryotic cell.

 

Experiment 1: Identifying Cell Structures

Post-Lab Questions

1. Label each of the arrows in the following slide image:

Structure Identity
A Click here to enter text.
B Click here to enter text.
C Click here to enter text.
D Click here to enter text.

 

 

2. What is the difference between the rough and smooth endoplasmic reticulum?

 

 

3. Would an animal cell be able to survive without mitochondria? Why or why not?

 

 

4. What could you determine about a specimen if you observed a slide image showing the specimen with a cell wall, but no nucleus or mitochondria?

 

 

5. Hypothesize why parts of a plant, such as the leaves, are green, but other parts, such as the roots, are not. Use scientific reasoning to support your hypothesis.

 

Experiment 2: Create a Cell

Post-Lab Questions

1. What cell structures did you place in the plant cell that you did not place in the animal cell?

 

 

2. Is there any difference in the structure of the two cells?

 

 

3. What structures do cells have for support in organisms that lack cell walls?

 

 

4. How are organelles in a cell like organs in a human body?

 

 

5. How does the structure of a cell suggest its function? List three examples.

 

6. In the table below, list the items you used to represent the various organelles in your ANIMAL cell. Provide a brief rationale explaining why you selected each item.

Item Organelle Rationale
Click here to enter text. Click here to enter text. Click here to enter text.
Click here to enter text. Click here to enter text. Click here to enter text.
Click here to enter text. Click here to enter text. Click here to enter text.
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Click here to enter text. Click here to enter text. Click here to enter text.
Click here to enter text. Click here to enter text. Click here to enter text.

 

7. Insert picture of your ANIMAL cell with your name and access code handwritten in the background.

 

8. In the table below, list the items you used to represent the various organelles in your PLANT cell. Provide a brief rationale explaining why you selected each item.

Item Organelle Rationale
Click here to enter text. Click here to enter text. Click here to enter text.
Click here to enter text. Click here to enter text. Click here to enter text.
Click here to enter text. Click here to enter text. Click here to enter text.
Click here to enter text. Click here to enter text. Click here to enter text.
Click here to enter text. Click here to enter text. Click here to enter text.
Click here to enter text. Click here to enter text. Click here to enter text.
Click here to enter text. Click here to enter text. Click here to enter text.
Click here to enter text. Click here to enter text. Click here to enter text.
Click here to enter text. Click here to enter text. Click here to enter text.
Click here to enter text. Click here to enter text. Click here to enter text.

 

9. Insert picture of your PLANT cell with your name and access code handwritten in the background.

 

 

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