Cellular Respiration Design-A-Lab
Yeast are eukaryotic organisms that are able to break down sugars to produce ATP. Some species of yeast are capable of surviving in both, aerobic and anaerobic conditions. This unique characteristic allows yeast to thrive in all sorts of environments, ranging from your intestines to the spongy dough we use to make breads.
Like all other living cells, yeasts must be able to produce ATP. As you know, glycolysis will occur without the presence of oxygen. Yeast cells will use glycolysis to produce some ATP, and will follow glycolysis with fermentation. Fermentation results in the production of CO2,
and alcohol:
glucose --> CO2 + C2H5OH
In this laboratory session you will be given a set of materials and you will be asked to design your own experiment. Your goal is to determine the effects of a variable of your choice on yeast cells. You will be using the carbon dioxide-producing capabilities of yeast to study their respiration. You will discuss your results in terms of your design.
Some of the variables that affect yeast respiration include
MATERIALS AND METHODS
The following is a list of available materials. You are by no means obligated to use all of them! Please feel free to propose other materials that might be useful to your group.
STEPS TO COMPLETE (during this period)
1. Use the attached sheet to design a controlled experiment that shows the effect of your chosen variable on yeast respiration. Make sure your experiment description includes the following:
a. A testable hypothesis. Remember hypotheses are written as “If…then” statements.
b. A detailed experimental design which will include at least five different test conditions plus a control
c. A data table for recording information
3. Write up a detailed experimental plan on the accompanying sheet of paper.
LAB WRITE UP
1. Methods/Procedure
Submit a past-tense, impersonal version of your lab protocol.
e.g. DO NOT USE: We are taking the temperature every 2 minutes. USE: The temperature was taken every 2 minutes.
2. Results
Use a table with an appropriate caption to present your results. Ensure that your results do not include inferences.
3. Analysis
a) Explain the purpose of fermentation in yeast. Why do they produce ethanol? Where is carbon dioxide produced? What happens to it?
b) Briefly, in paragraph form, explain the role of anaerobic respiration and “oxygen debt” in Homo sapiens .
c) How does this relate to the Exercise Lab we worked on? Explain your groups’ results in light of what you now know about cellular respiration.
d) Using the examples of (choose one) diet, use of pharmacological substances, or mitochondrial diseases, provide a one-page justification for the statement:
“Knowledge of metabolic processes is relevant to personal choices.”
4. Conclusion
Provide a paragraph-form explanation of your results, highlighting their tie to cellular respiration. Was your hypothesis correct? Based on your results, formulate a new (testable) hypothesis. If you were to redo this lab, what would you have done differently? Suggest three ways to improve this lab.
5. Bibliography
Name __________________________
EXPERIMENTAL DESIGN GUIDE
Teacher Approval_________
TITLE
HYPOTHESIS (If...then)
INDEPENDENT VARIABLE
MEASUREMENT OF INDEPENDENT VARIABLE
NUMBER OF TRIALS
DEPENDENT VARIABLE
MEASUREMENT OF DEPENDENT VARIABLE
CONTROL
Presenting a Formal Lab Report
Science involves the extensive use of experiments to observe the world around us. Working scientifically involves being precise and accurate when making and interpreting observations. Once the observations are obtained, conclusions can be drawn from them. A laboratory
report is a method of clearly presenting one’s experimental work and its possible conclusions to others. A good lab report is precise & well-organized. It should explain:
1. Why the experiment was conducted 2. How it was done
3. What happened 4. What the results can mean
There are many formats for a lab report. We will be using the following: 1. Purpose
Use complete sentences to explain the purpose of doing the experiment (ex. To determine which laundry detergent most efficiently removes tomato stains.)
2. Hypothesis
This is an educated guess that predicts the results (ex. Tide with Bleach will be the best at removing the tomato stains.)
3. Materials
Provide a detailed list of all of the materials used in the experiment. (ex. water, 60 mL of each detergent, tomato-stained napkins) A diagram can be used to show the experimental set-up.
4. Methods
Use numbered steps clearly written in full sentences to describe, in past-tense, how the experiment was done. This should not be a word-for-word repetition of your protocol – you are to describe what you DID, not what you were supposed to do.
5. Observations
Observations should be complete and indicate only what you saw (no inferences!). They should be organized (using a table, diagram, graph, quantitative or qualitative) and should include the relevant units of measurement. They SHOULD NOT include calculations. 6. Analysis
Cellular Respiration Lab
___ THE SUBMISSION IS WRITTEN IN YOUR OWN WORDS
* if you plagiarize (copy word-for-word) in your submission you will receive a zero (0) for that section; if you plagiarize more than 1/3 of the content of your presentation you will receive a zero (0) for the ENTIRE submission
A1. demonstrate scientific investigation skills (related to both inquiry and research) in the four areas of skills (initiating and planning, performing and recording, analysing and interpreting, and communicating);
the experimental design is clear and presents a logical sequence for the experiment in-class explanation was well prepared
a data table is present and used for recording information the table has a relevant captions
at least two references are used and are presented in an appropriate format (Bibliography Worksheet), paraphrasing/direct quotations are used judiciously
grammar is correct
the rubric was used to evaluate own work
mark*: 4 3 2 1 R mark: 4 3 2 1 R
C1. analyse the role of metabolic processes in the functioning of biotic and abiotic systems, and evaluate the importance of an understanding of these processes and related technologies to personal choices made in everyday life;
Explanations of connection between everyday life and metabolism is well done, with thorough explanations of roles of metabolism in results and in everyday life
information makes sense and is correct key words and ideas are correctly used complicated vocabulary is explained/ defined mark*: 4 3 2 1 R mark: 4 3 2 1 R
C2. investigate the products of metabolic processes such as cellular respiration and photosynthesis; Results are interpreted in view of the function of cellular respiration
Lab is adequately designed
information makes sense and is correct key words and ideas are correctly used complicated vocabulary is explained/ defined mark*: 4 3 2 1 R mark: 4 3 2 1 R
C3. demonstrate an understanding of the chemical changes and energy conversions that occur in metabolic processes. Results are interpreted in view of the function of cellular respiration
information makes sense and is correct key words and ideas are correctly used complicated vocabulary is explained/defined mark*: 4 3 2 1 R mark: 4 3 2 1 R
*4 (excellent), 3 (good), 2 (satisfactory), 1 (needs improvement), R (incomplete, please resubmit)
Notes to teacher:
- prepare the yeast: dissolve a reasonable amount of dry yeast in 40 oC water, right before the lab
- prepare sugar solutions using molarity of sugars, at 0.5 mol/L - sucrose 342.2965 g/mol 17 g/100 mL
- fructose 9 g/100 mL
- sugar solution made to 0.5 M, 17 g/ 100 mL for disaccarides, 9. g/ 100 mL for monosaccharides
- prepare NaOH/HCl solutions + 1.0 M sucrose to test (or fructose if available: preferred)
per station - test tube rack
- 6 test tubes (regular)
- 6 test tubes (small: these should hold 10 mL) - wax pencil
- pipette - stirring rod
- thermometers
- hot plates (4: 2 for experiment, 1 for warming yeast, 1 for keeping warm water) - ice
shared - detergent
- test tube brushes
variables:
- temperature: ice, room, 40, 60, 80 - carbohydrate concentration
- carbohydrate type - acidity/alkalinity - yeast concentration
