Get help from the best in academic writing.

Experiment to Explore the Rate of Fermentation

Biology: Respiration, fermentation
GLX setup file: grape juice.glx
Qty
Equipment and Materials
Part Number
1
PASPORT Xplorer GLX
PS-2002
1
PASPORT CO2 Gas Sensor
PS-2110
1
PASPORT Extension Cable
PS-2500
1
PASPORT Fast-Response Temperature Probe (included with GLX)
PS-2135
1
Sampling Bottle (included with sensor)
1
Balance
SE-8723
1
Beaker, 1 L
SE-7288
1
Beaker. 250 mL
1
Graduated Cylinder
SE-7289
1
Hot Plate
SE-8767
1
Magnetic stirrer with stir bar
5 mL
Mineral oil
1
Pipette
1 g
Sodium fluoride, solid
1 pkg.
Yeast, dry
1 L
Water
1
Weighing paper
Purpose The purpose of the activity is to explore the rate of fermentation. Measure the production of carbon dioxide gas in a sampling bottle containing yeast and grape juice and then measure the gas production when a chemical inhibitor is added to the grape juice/yeast mixture.
Background All organisms require a source of energy to maintain cell physiology and growth. Cellular respiration is the process utilized to oxidize food molecules and release the energy to fuel life processes.
There are two types of cellular respiration – aerobic and anaerobic – and both begin with glycolysis. Glycolysis is a biochemical process utilized by most microorganisms (yeast, bacteria) and “higher” animals to convert glucose to pyruvate and adenosine triphosphate (ATP). Prior to glycolysis, enzymes break down starch into complex sugars (such as sucrose) and then simple sugars (such as fructose and glucose). During glycolysis, the glucose breaks down into pyruvate.
Animal cells and some unicellular organisms convert the pyruvate to lactic acid (lactic acid fermentation). Some plant cells and unicellular organisms convert the pyruvate to ethanol and carbon dioxide gas (alcoholic fermentation).
Yeasts are versatile organisms. Unlike most other organisms that obtain their cellular energy either through aerobic respiration (requiring gaseous oxygen) or through anaerobic respiration – fermentation – (requiring the absence of oxygen), yeast cells respire in either condition, depending upon the availability of gaseous oxygen.
During fermentation, enzymes break down complex carbohydrates into simpler ones. The loss of structural integrity, which can result from changes in pH or high temperatures, usually leads to a loss of enzyme activity.
In this activity, the yeast cells use fermentation(also known as anaerobic respiration) to transform the sugars in grape juice into carbon dioxide gas, ATP molecules, and ethanol.
Pre-lab Questions Measure carbon dioxide gas production during the metabolism of yeast in grape juice.
How would a chemical inhibitor that stops enzyme actions affect the carbon dioxide gas production?
How would a change in temperature (either very cold or very hot) affect the carbon dioxide gas production?
How will the gas production change over time?
Safety Precautions Follow all directions for using the equipment.
Wear protective gear (e.g., safety goggles, gloves, apron).
Procedure Yeast and Grape Juice Preparation
Connect a Fast-Response Temperature Probe (included with the GLX) into Port 1 on the left side of the Xplorer GLX. The Graph Screen will automatically open with Temperature (ËšC) versus Time (s).
Press the Home key () to go to the Home Screen. Select ‘Digits’ and press the Activate key ().
Pour 450 mL of grape juice into a beaker. Put the end of the temperature probe into the juice. Press the Start key () on the GLX so you can watch the temperature of the grape juice.
Place the beaker on a hot plate and slowly warm the juice to a temperature of 30 to 35ï‚°C (yeast will die above 40°C). When the temperature is between 30 and 35°C, adjust the hot plate so the grape juice remains warm, but does not get any hotter.
While the juice is warming, add 100 mL of warm tap water to another beaker. [Remember to keep the temperature below 40ï‚°C – use the temperature probe to make sure.] Add a package of dry yeast to the beaker and stir well. The yeast will become active in 15 to 20 min.
GLX Setup
Stop recording temperature data. Remove the Fast-Response Temperature Probe from the GLX.
Connect a PASPORT Extension Cable into Port 1 on the top of the Xplorer GLX. Connect the other end of the Extension Cable to the PASPORT CO2 Sensor. The Graph Screen will automatically open with CO2 Concentration (ppm) versus Time (s).

Open the GLX setup file labeled grape juice.glx (check the appendix at the end of this activity). The file is set to record data once per second.
Sensor Calibration (Optional)
See the appendix at the end of this activity.
Equipment Setup
Transfer 150 ml of warmed grape juice to the sampling bottle. Add a stir bar.
Mix the yeast suspension well and add 10 mL to the juice.
Use a dropper to add a layer of mineral oil to the surface of the grape juice/yeast mixture so the yeast will have anaerobic conditions.
Put the end of the CO2 Gas Sensor into the sampling bottle loosely. (You do not want gas pressure to build up too high in the sampling bottle.) Do not push the rubber stopper down into the end of the sampling bottle. Note: Avoid bumping the CO2 Gas Sensor during data collection because it may record erratically.

Put the sampling bottle on the magnetic stirrer. Turn on the stirrer.
Record Data: Grape Juice and Yeast
Press the Start key on the GLX.
Record data for 30 minutes and then stop.
Carefully remove the CO2 Gas Sensor from the sampling bottle. Dispose of the contents as directed and rinse the inside of the bottle.
Record Data: Grape Juice, Yeast, and Inhibitor
Transfer another 150 mL of warm grape juice to the sampling bottle and add 1.0 g of sodium fluoride.
Stir the yeast suspension again and add 10 mL to the grape juice. Add a layer of mineral oil on top of the grape juice as before.
Return the CO2 Gas Sensor to the sampling bottle so that the rubber stopper rests loosely in the end of the bottle.
Press the Start key on the GLX, record data for 30 minutes and then stop.
Carefully remove the CO2 Gas Sensor from the sampling bottle. Dispose of the contents as directed and rinse the inside of the bottle.
Record Data: Warm Grape Juice and Yeast
Disconnect the CO2 Gas Sensor and reconnect the Fast-Response Temperature Probe. Select ‘Digits’ as before and put the end of the probe in the remaining grape juice.
Use the hot plate to warm the grape juice to between 45 and 50ËšC. Transfer the warmed grape juice to the sampling bottle.
Stir the yeast suspension again and add 10 mL to the warmed grape juice. Add a layer of mineral oil on top of the grape juice as before.
Disconnect the temperature probe and re-connect the CO2 Gas Sensor. Return the CO2 Gas Sensor to the sampling bottle so that the rubber stopper rests loosely in the end of the bottle.
Press the Start key on the GLX, record data for 30 minutes and then stop.
Carefully remove the CO2 Gas Sensor from the sampling bottle. Dispose of the contents as directed and rinse the inside of the bottle.
How do your results compare with others in your class?
Analysis Draw a sketch of your CO2 concentration versus time graph as requested in the Lab Report section.
Use your recorded data to find the change in CO2 concentration for the grape juice and yeast, the grape juice, yeast, and inhibitor, and the warmed grape juice (optional). In the Graph Screen, press F3 to open the ‘Tools’ menu. Select ‘Statistics’ and press ‘Activate’. The Statistics show the minimum and maximum values.

Calculate the rate of change of CO2 concentration versus time, or the ratio of CO2 concentration (in ppm) divided by the time (in minutes), for each run of data.
Record your results in the Lab Report.
———————— Appendix: To open a specific GLX file, go to the Home Screen (press ). In the Home Screen, select Data Files and press the Activate () key. Use the cursor keys to navigate to the file you want. Press F1 () to open the file.
Optional: To calibrate the PS-2110 CO2 Gas Sensor, see the instructions provided by the instructor.
Name ________________________________ Date ___________ Pre-Lab Questions Measure carbon dioxide gas production during the metabolism of yeast in grape juice.
How would a chemical inhibitor that stops enzyme actions affect the carbon dioxide gas production?
How would a change in temperature (either very cold or very hot) affect the carbon dioxide gas production?
How will the gas production change over time?
Data Make a sketch of one run of CO2 concentration versus time, including labels for the y- and x-axes.
Data Table Run
Initial CO2 (ppm)
Final CO2 (ppm)
Total time (min)
CO2 production (ppm/min)
Grape juice yeast
Grape juice, yeast, inhibitor
Warm grape juice yeast
Questions What is the overall rate of CO2 production for grape juice and yeast and how does it change over time?
How does the rate of CO2 production for grape juice, yeast, and the chemical inhibitor compare to the rate for the grape juice and yeast alone?
How does the rate of CO2 production for the heated grape juice and yeast compare to the rate for the grape juice and yeast?
What can you conclude about the affect of the chemical inhibitor on the yeast suspension?
What can you conclude about the affect high temperature on the yeast suspension?

Guide to Writing Lab Reports

Aspect 1: Defining the Problem and Selecting Variables: Research Question (RQ)
The first part of planning an experiment is writing a good research question that you will investigate.
A Good RQ will:
Include both dependent and independent variables
Be Quantitative if appropriate
Include the organism or tissue investigated
Hypothesis
A hypothesis is a statement that addresses the RQ and makes a prediction about what will happen.
A Good Hypothesis will:
Be written in an “If. . ., then. . ., because. . .” format.
(If the [independent variable] [does something], then the [dependent variable] will [do something as a result], because [explanation].)
Include both dependent and independent variables
Be Quantitative if appropriate
Be Testable (Falsifiable)
Relate to the RQ
Be explained
Variables
Variables are the different parts of your experiment that are able to change from one experiment to another. In order to perform a fair test it is important to make sure that we control as many variables as possible in order to gain accurate data.
A Good Variables list will:
Include the Independent variable – the variable you change
Include the Dependent variable – the variable that changes as a result of the independent variable
Include other Controlled variables (constants?) and why we need to
Identify the control (controlled variables are things we need to keep constant in each experiment)
Groups:
These groups should be very clearly identified so that you may refer back to them throughout your lab report as you do data processing, data presentation, and your conclusion/ evaluation.
Control group: This is the baseline group that you will be comparing the how the independent variable affects the dependent variable. This is NOT the same thing as controlled variables.

Experimental group(s): This (These) is (are) the what is affected by the independent variable and is what you are measuring.
Aspect 2: Controlling Variables: Control of Variables
Part of methods section of a lab is to include how you will control the variables, not simple what the variables are as listed above. It is possible to list the variables in the method section or to list them in their own section before materials and methods. If this is the case you will still need to discuss HOW you will control them in the methods section.
A Good Control of Variables section will:
Specify how the measurements will be collected.
Specify how the other variables will be controlled.
Make sure that each variable in the list is mention
Aspect 3: Developing a Method for Collecting Data: Apparatus and Materials
Includes the necessary equipment and materials to control and measure the variables listed in Aspect 1. Should be in its own section separate from Method.
A Good Apparatus and Materials List will:
Indicate the correct materials for each variable
Indicate the precision of measurements: ‘500 ml beaker’, instead of just ‘beaker’
‘Thermometer (0-100°)’ instead of just ‘Thermometer’
‘1 meter stick’ or ‘100 cm ruler’ not just ‘ruler’

Can include an annotated diagram, but not necessary
Methods to Collect Sufficient and Relevant data
Includes a numbered series of steps to control all variables and collect sufficient and relevant data. It is important when planning an experiment to think about the RANGE and SIZE of measurements as well as how many REPLICATES of the experiment you will do. This is part of the methods section. Should be in its own section separate from Apparatus and Materials
A Good Methods section will:
Include all steps necessary to complete the experiment (even the obvious ones- think about your grandma)
Include how and when to take measurements or record observations
Address an appropriate RANGE of intervals or measurements.
i.e. temperature from 0-10 or 0-100 or 50-100, etc
IB requires that you have a minimum of 5 increments (or trials) with a minimum of 5 repeats at each trial.
Address the SIZE of intervals or measurements
i.e. what units of time will be used, or how long will the experiment run, etc
Indicates how many times the experiment will be REPLICATED
i.e. how many times should you do the experiment?
Makes sure that relevant data is able to be collected
Data Collection and Processing Aspect 1: Recording Raw Data:
Collecting and recording raw data
Data collection skills are important in accurately recording observed events and are critical to scientific investigation. Data collection involves all quantitative or qualitative raw data. Qualitative data is defined as things being observed with more or less unaided senses (color, change of state, etc.) or rather crude estimates (hotter, colder, brighter, etc). Quantitative data involves some measurement.
A Good Data Collector will:
Record all appropriate data
Pay attention to detail
Include units for all measurements
Include uncertainties of the instruments used
Rules for data table construction
It is important when presenting data that is done in an effective and easy to read format. There are more than one ways to make a table, but you should always follow convention when making your tables.
A Good Data Table will have:
A descriptive title
Headings with units, no units in body of table
Independent variable in the left hand column
Dependent variable across the top
Uncertainties in all measurements
Whenever we make a measurement we do so with some error or uncertainty. We cannot make exact measurements, therefore it is important to indicate what level of uncertainty there may be. This should be done in the headings after the units are given.
Uncertainties are calculated as:
± ½ of the smallest unit measurable by the instrument. For example, a thermometer that is graded to 1°C has an uncertainty of ± 0.5°C
± 1 unit of length (½ x 2 measurements)

Aspect 2: Processing Raw Data:
Data Processing
Data processing means that you are actually converting the data into another form. Putting numbers into a table is not data processing!
A Good Data Processing section will:
Show the formula you used, even if it seems simple
Include processes such as: means
standard deviations
% differences
Statistical tests
t-test
X2 (Chi-squared) test

Aspect 3: Presenting Processed Data:
Data Presentation
Data presentation is not always necessary to every lab. You must evaluate if the data you collected is able to be graphed. [Hint: basically all quantitative data can be collected]
A Good Data Presentation section will:
Use the appropriate graph type: continuous variable – best line or scatter graphs
discontinuous variable – bar graphs
parts of a whole – pie charts

Have a descriptive title
Have appropriate headings with units on both axis
Be drawn neatly with axis being drawn in pencil
Have clear labels or a key if more than one data set is present on one set of axis
Have clearly marked and appropriate units
Have points clearly located and marked
NEVER ‘connect the dots’!!!
Aspect 1: Concluding:
Conclusion:
A conclusion is not simply a restatement of the problem. It requires thought and analysis of the relevant data collected and presented.
A Good Conclusion will:
Refer back to the RQ and hypothesis. Remember, you CAN NOT ‘prove’ your hypothesis right. You can support it, or disprove it, but you cannot prove anything!
Be explained with reference to data analysis and literature values [translation: don’t say something that is not in your data!]
Give the quantitative relationship between variables where appropriate – linear, exponential, inverse, positive, negative, not ‘it changed’, we can see that! Say how it changed!
Compare results with text book or other literature values
Aspect 2: Evaluating the Procedure:
Evaluation:
Most difficult part! You are not being judged as person, so don’t take the defensive and try and justify your mistakes! Be honest, and think hard about what you could have done better.
A Good Evaluation will:
Identify sources of error in method and measurement
Identify limitations in method [whether or not you chose it or not] and data collection
Aspect 3: Improving the Investigation:
Improvements:
After you identify possible sources of error in your experiment it is necessary to provide realistic methods to improve on your experiment.
A Good Improvements section will:
Address each of the possible sources of error in the investigation and cite methods that could be used to fix them
Change – don’t say the temperature changed, or the graph changed. Use increase or decrease, or another qualitative statement.
‘It’, ‘They’, ‘Them’ – use nouns. It doesn’t matter if you say the same thing 100 times! This is not English class.
‘Prove’ – You can’t prove anything. You can only support your hypothesis.
SO. . . ‘The temperature changed, therefore it changed too, which proves my hypothesis to be correct.’ Is a horrible sentence!

[casanovaaggrev]