Principles of Biology

Description

Lab 5 Cell transport osmosis experiment  

Purpose:  You will examine the process of osmosis using a cell model of Gummi bears to measure changes in the cell. This lab allows you to practice multiple skills in the completion of the osmosis experiment. These skills include: forming a hypothesis and making prediction, setting up an experiment and collecting data, making a data table and drawing a bar graph, using the data to make a conclusion about the results.

Learning outcomes:

• Be able to form a hypothesis and test the hypothesis
• Be able to write a plan with steps followed to complete the experiment
• Be able to draw a table that is correctly labeled with titles and units and fill it with collected data
• Be able to calculate an average of data collected
• Be able to draw a properly labeled bar graph of averaged results
• Be able to analyze data and write a summary of the results that includes an overall conclusion

Why you are using Gummi bears as cell model in this experiment:

Gummi bears are a sugar and gelatin-based candy that may be used to model the movement of water into cells (prokaryotic and eukaryotic) by the process of osmosis. Gummi bears are made mostly of plant materials: corn syrup, sugar, Dextrose, Citric Acid, Starch, Coconut Oil, Carnauba Wax, Beeswax Coating, Artificial & Natural Flavors and Colors, with some gelatin (animal source) and they contain a very small amount of water so that when placed in watery environment osmosis may occur readily and result in changes in the Gummi bear shape and texture. These changes are measurable.

General instructions:

Work as an individual or in a team of 2 students maximum. You are to form a hypothesis about osmosis and cells (using Gummi bear as the cell model) then you will design and run an experiment to test your hypothesis. Using six Gummi bears in the experiment, you will collect data for each bear and record in a data table. Since 6 gummi bears are used it will be best to average the results so that a summary of before and after may be reviewed in the data.  Averaging results reduces the variation that occurs using different samples. The measurements will be in metric units: grams (g) for mass, centimeters (cm) for length and/or width. Finally the data will be visually presented in a Bar graph using appropriate labeling and scaling. This data will be reviewed and you will write a conclusion about what your experimental findings.  The conclusion is always a summary of the results and may or may not support the hypothesis you have proposed.

Note: It is assumed this work will be your own and will not be another person’s work since that is plagiarism. Plagiarized work will need to be revised and if not will receive 0 grade.

 

Guidelines on how to set up the experiment:

Determine the data you will need to collect ahead of the experiment. There must be a “before soaking” set of data points and an “after soaking” set of data points so these data sets may be compared. However you decide to measure the data on each gummi bear, record your data points in a data table with units and proper labeling. For example: collect mass changes by weighing each gummi bear on a kitchen scale in recording the mass units in grams (not pounds or ounces). Alternatively, if you do not have a kitchen scale then collect length and width measurements in units of centimeters using a metric ruler.

Here is an example of a properly labeled data table with title and units:

Gummi bear	Presoak mass (g)	Post soak mass (g)	Average of gummi bears (g) to be graphed
1	17.0	35.5	Pre-soaked 17+17.5/2=17.25=17.3
2	17.5	25.0	Post-soaked 35.5+25=60.5/2 =30.25=30.3

 

Perform the experiment one time. Collect the before soak and after soak data for each individual Gummi bears and record this information in a data table. Calculate the average of the presoak and post soak data collected from the 6 Gummi bears and record the averaged value in the data table as separate entry.

See link to learn how to average: https://www.mathsisfun.com/mean.html. This averaged data is what is to be graphed so there will be only two bars in the bar graph.

 

Materials you will need to assemble for the experiment:

• Gummi bears – 6 individual gummi bears. One bag may be purchased at a dollar store for $1.00.
• Kitchen scale – Use scale if you have one available. Measure the mass in grams for each individual gummi bear before and then after the experiment. If you do not have a kitchen scale then use a metric ruler. See next entry below.
• Metric ruler – Use ruler if you do not have scale available. Measure the size of the gummi bear before and after for comparison. Use centimeters as unit of measure. Determine how you want to measure the gummi bear and use this method consistently before soaking and after soaking for each gummi bear
• Tap water – use plain water from the faucet. You do not need to purchase water. Use enough water to cover each Gummi bear completely with water.
• 6 cups or containers or zip lock bags – plastic, glass, ceramic. Use what you have on hand and they do not need to be the same size. Use one container for one Gummi bear.
• Find a location to store the Gummi bears undisturbed for one day (24 hours) at room temperature. Allow Gummi bears to soak 24 hours minimum, maximum 48 hours
• Use your cell phone to take 4 pictures at specific points during the experiment. The pictures are to be inserted into the final typed report and labeled as follows:

Picture 1. A picture of the experimental set up

Picture 2.  A picture of the instrument used to measure the Gummi bears (ruler or scale)

Picture 3.  A picture of the 6 pre-soaked Gummi bears

Picture 4.  A picture of the 6 post-soaked Gummi bear

 

 

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What do I turn in, where do I turn in my work and when is this lab report due?

Type the report in Microsoft word with the specific information shown below then upload to Assignment Lab 5 located in the Lab 5 subfolder. The report must have the following items in it to receive a high score:

1. Your hypothesis
2. Your prediction based on the hypothesis
3. Explanation of how experiment was set up and run to test your hypothesis. Include what was measured in the Gummi bears and the instrument used to do this measurement.

This is where you will insert Picture 1 experimental set up.

4. Run the experiment once and record the data in a data table. Make sure and include before soaking measurements, after soaking measurements, units of measurement used, and averaged data column (this last part is added after the experiment is completed).

This is where you will insert labeled Picture 2 showing the instrument you used to measure the changes in Gummi bears.

This is also where you will insert labeled Picture 3 of pre-soak Gummi bears.

This is where you will insert labeled Picture 4 of post-soak Gummi bears.

5. Draw a bar graph of averaged data results. You may draw the bar graph by hand or use Excel. Your bar graph is inserted into the lab report. Graph should have the x- and y-axes labeled with units of measurement, and sample name. See link for making graph and table: https://youtu.be/vatJYQEV-qA
6. Look at your results and summarize what happened in the experiment and write a final statement or conclusion in your report.
7. Upload your completed report to Assignment Lab 5 by Sept 15 11PM. If the similarity score is high (more than 30% and/or red color) then you will need to revise your report so that it is showing your own work and not the work of someone else then re-upload.