Enzymes lab
Name: _______________________________
Print this lab, follow directions and answer all questions neatly in the worksheet that follows this lab. Once completed, save the
LAB_WORK SHEET with your last name & submit within Work2Do tab. Be sure to save your document as LASTNAME_lab5. My last
name is Ashraf, so my file would be named Ashraf_lab5.
Getting Started—How to Use the Online Enzyme Lab
This lab has three parts so plan your time accordingly! (Note: the lab is weighted as two lab grades because it is so long)
Opening the lab:
A. Go to http://biologylab.awlonline.com. If you are a first-time user, you must register with the site. Make sure you have your lab
pass code around when you do this. Also, be sure to write down the login and password you create for your account.
B. Click on "Enzyme Lab" to access the online lab once you have registered.
Feel free to read the introduction and the background information. Keep
in mind that these online labs were developed so the publisher could get
the most bang for their buck. . . so this lab was written to accommodate
biology students ranging from introductory students such as yourself to
senior-level biology majors (in other words, don't expect to understand all
of the verbage on the pages !
C. Click on the "Start Lab" button to open the interactive laboratory. Be
patient as the lab loads - it may take a little time. Also, contact the
instructor if you cannot get the interactive laboratory to load. Once you
have the lab open, it should look like the image to the right.
D. Familiarize yourself with the virtual lab materials you will be using by clicking on each item on the lab bench. You’ll see a
description of the item pop up in the upper right hand corner.
Question 1: List all of the virtual lab materials in this lab, and in your own words, give a brief description of what they are used for or
do. Write your answer in the write-up worksheet only!
E. Once you've familiarized yourself with the lab materials, click
on the "Experiment" button on the left hand side of the
window. A screen should appear that looks like the picture to
the right.
On this screen, you will be able to change a number of
variables, including pH, temperature (in Celsius) and
substrate concentration ([S]). There is also a place to change
inhibitor concentration [I], which you won't be doing unless
you choose to do the extra credit at the end of this lab.
Changing Temperature: To change the temperature, use
your mouse to highlight the temperature value (see red
arrow in picture to the right) and type in a new value. The range the lab window will accept is from 30-80°C.
Changing pH: To change the pH of the buffered solution your enzyme is in, click on the pH box (see blue arrow in above picture),
and scroll to select the desired pH. The available pHs of the buffered enzyme solutions range from pH3 - pH10.
Changing Substrate Concentration, [S]: To change the substrate concentration (the concentration of sucrose you will be
providing for the invertase), either use your mouse to pull the [S] bar either left or right (see purple arrow in above picture), or
select the [S] value in the text box (to the right of the [S] bar), type in a value and press enter. Substrate concentrations the
window will accept range from 0 to 1000 mm (mm means millimolar, which is a unit for concentration).
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F. For this first run, set the temperature at 30°C, the pH at 5.0 and the [S] at
200, then click “add enzyme and go!”
The window should start collecting data for you and plot it on a graph.
Once data has been collected, it should look something like the picture
to the right (your data points may be higher or lower on the graph since
each run is unique).
G. Once you've collected data, you aren't done yet! Next (and this is a
REALLY important step), you need to "fit" your data using the movable
red bar in the graph window. Use your mouse to select the red bar, and
then drag it until it overlaps your data points pretty well. You will notice
the "Slope" listed changes (and should be somewhere around 0.0014, if
you'd like to check if you did it right for the experimental conditions
listed above). The second picture on this page shows you how to fit the
slope to the data points for my run.
Great work so far! At this point you have successfully completed one
trial run of your experiment! The next step is data collection. The
window is set up such that by pushing a button, the window it will
collect data for you and allow you to eventually download the data onto
your computer. It even makes tables for you!
H. To collect data, you’ll tweak your pH, temperature and *S+ (see below), then click “add enzyme and go.” Then, you’ll fit the slope
(red line) to your data points and—THIS IS IMPORTANT!—click on
to record your run. If you don’t hit the
record data button, your data are lost (And yes, the word “data” is plural, as in, you recorded multiple points on the graph. The
singular for data is “datum.”)
Once you've recorded your data and are ready to do your next experimental run, click on
and start
again. Be sure to use the "Clear Experiment" button to reset the screen. DO NOT CLOSE THE WINDOW ENTIRELY OR YOU WILL
LOSE ALL OF YOUR RECORDED DATA!
OK - now that we know the basics of how to work with this on-line lab, it's time to get going with some experiments. Remember
to email me if you have any questions!
Experiment 1: How will temperature influence invertase activity?
I. Form an hypothesis: Determine how temperature influences the speed at which invertase breaks down sucrose. Ask yourself
"How will temperature influence invertase activity?" by first developing a testable hypothesis. Write down your hypothesis as
the answer to Question 2 on your lab write-up worksheet. Write your answer in the your lab write-up worksheet only!
J. Develop a method: After you've written an hypothesis, next you will need to develop the method you will use to test your
hypothesis. As a hint, you will want to change only one variable in this experiment—temperature—and leave all other values
constant.
Also, it's good to pick middle-of-the-road values for the variables you plan to leave constant (for example, consider using pH = 7
and [S] somewhere around 500mm). Finally, as you develop your method, you will want to make sure that you plan for enough
test runs to test the entire range of temperatures available to you (from 30-80°C ). Consider changing the temperature by 5 to
10 degree increments starting at 30°C and ending at 80°C. Write down your method as the answer to Question 3 on your
worksheet.
K. Carrying Out Your Experiment: Next, carry out your experimental method, being sure to fit your data with the red line as well as
recording your data with the "Record Data" button after each trial run. We will learn how to look at recorded data in the next
section. (As a note, there is no need to change the "Experiment #" on the virtual lab window until after you finish collecting all of
your temperature data). Once you have finished collecting all of your data, move on to the next step.
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L. To view your recorded data, click on “Plot data” in the upper left hand
corner of the lab screen. The window which then appears lists all of the
data you collected in a spread sheet. Save this data to a place where you
can copy and paste it into your word processor document by clicking on
the "Add to Notes” button right now. The window that pops up shows
your data and allows you to highlight the data, then copy and paste it into
a word document (don’t worry about copying and pasting yet—we still
have more data to collect). Keep your "Lab Notebook" (see picture at
right) open as you work, as you will be adding to it throughout the rest of
this lab.
M. Once you've added your table of data to your lab notebook, next you will
want to plot you data to see what it looks like. On the Virtual Laboratory window (probably behind the notebook window at this
point), select what type of graph you would like to plot (see second picture on the right). Select the plot type you feel is most
appropriate for the data you collected (by the way, [V] represents how fast
the enzyme worked in your experiment, and stands for velocity). Note: the
picture at the right does not look like what yours probably will because I
did not run enough data points to get a complete picture of activity at
different temperatures.
N. Next, you will want to select which data you would like to plot by holding
down on your "CTRL" button on your keyboard, and selecting the lines of
data you would like to plot. You can select all of your data this way, or if
there was a test run you made a mistake on, you can omit it from your
graph by not highlighting it (see below). Once you have selected all the
data you would like to plot, click on the "Plot Selected Data" button. If you
get an error message instead of a graph, select a different “Plot Type” and
try again.
O. A plot of your data should appear. Click anywhere on the plot and you will see an arrow appear on the Temp line at the bottom.
Drag this arrow until it lines up with the point on the graph where you feel the invertase was working the fastest. Once you've
found that point on the graph, click on the "Add to Notes" button (this will bring your lab notebook back up). Analyze your data
and draw conclusions about your experiment by answering Questions 4, 5 and 6 in your worksheet.
You can delete your temperature data from the "Lab Notebook" once you have saved it into your worksheet. Now let’s move on to
the next experiment.
Experiment 2: How will pH influence invertase activity?
P. Develop a hypothesis: For this experiment, you will be carrying out a process similar to your temperature experiment, but instead
you will be testing the effects that different pH buffers have on the speed at which invertase breaks down sucrose. As you know
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from our review of chemistry, buffers are chemicals that are able to maintain the pH of a solution at a fairly constant value.
Different combinations of chemicals can create buffers which keep the pH of a solution at different pHs, so you can get buffers
for nearly any pH value you want. In this lab, the pH values available for you to use range from pH 3 to pH 10.
Develop a testable hypothesis to predict how pH will influence the rate at which invertase breaks down sucrose (Question 7 on
the worksheet). Be sure your hypothesis is testable!
Q. Develop a Method: Next, develop and type up the method you will use to test your hypothesis (Question 8 on the worksheet). As
you develop your method, keep in mind that although there are a number of pH values available for you to choose from, you
need not collect data for every single one. Vary the pH values you use by 0.4 to 1 pH unit between experimental runs, and be
sure to test the full range of pH values.
R. Carrying Out Your Experiment: Next, carry out your experimental method, being sure to fit your data with the red line as well as
recording your data with the "Record Data" button after each trial run. Once you have finished carrying out your experimental
method, and have collected all of your data, move on to the next step.
S. Accessing and Interpreting Your Data: Click on the "Plot Data" to look at the data you collected. Save your data into your Lab
Notebook by clicking on the "Add to Notes” button. Graph your data by following the same general steps as before (be sure to
select a plot type appropriate for the data you just collected). Once the data has been plotted, move the arrow bar with your
mouse to the point where you feel the invertase was working the fastest, and click on the "Add to Notes" button. Also, analyze
your data, draw conclusions about your hypothesis and cut and paste your table and graph into the worksheet (Questions 9, 10
and 11 on the worksheet).
You can delete your pH data from the "Lab Notebook" once you have saved it into your worksheet. Then, move onto the final
experiment.
Experiment 3: How will [S] influence invertase activity?
T. Develop an hypothesis: For this experiment, you will be carrying out a process similar to the last two experiments, but instead
you will be testing how sucrose concentration [S] effects the speed at which invertase breaks down the sucrose. Develop an
hypothesis related to how you think adding more or less sucrose to the reaction will influence how fast invertase breaks down
the sucrose (Question 12 on the worksheet). As before, your hypothesis does not need to be correct, but it does need to be
clearly explained. Write your answer in the worksheet only!
U. Develop a Method: Next, develop and type up the method you plan to use to test your hypothesis (Question 13 on the
worksheet). As you develop your hypothesis, keep in mind that although there is a large range of substrate concentrations for
you to choose from (0 to 1000 mm), you need not collect data for every value. Vary the [S] values you use in increments of 50 to
100 mm between experimental runs, and be sure to test the full range of values.
V. Carrying Out Your Experiment: Next, carry out your experimental method, being sure to fit your data with the red line as well as
recording your data with the "Record Data" button after each trial run. Once you have finished carrying out your experimental
method, and have collected all of your data, move on to the next step.
W. Accessing and Interpreting Your Data: Click on the "Plot Data" to look at the data you collected. Save your data into your Lab
Notebook by clicking on the "Add to Notes” button. Graph your data by following the same general steps as before (be sure to
select a plot type appropriate for the data you just collected). Once the data has been plotted, move the arrow bar with your
mouse to the point where you feel the invertase was working the fastest, and click on the "Add to Notes" button. Also, analyze
your data and draw conclusions about your hypothesis from it. Also, analyze your data, draw conclusions about your hypothesis
and cut and paste your table and graph into the worksheet (Questions 14, 15 and 16 on the worksheet).
You can delete your [S] data from the "Lab Notebook" once you have saved it into your word processor document.
Last, answer the summary questions on the worksheet (Questions 17, 18 and 19).
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