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Project 4.1.4: Dose Response
In Activity 4.1.1, you learned that environmental toxins can enter the human body via three main
routes of exposure – ingestion, inhalation, and absorption through the skin. Protection from
harmful chemicals can only occur by blocking these routes of exposure.
All chemicals in the environment, natural or man-made, can be toxic when present in high enough
concentrations. The science of toxicology aims to quantify the effects of toxic substances on living
organisms. Toxicologists work to determine how much of a chemical you can be exposed to
without experiencing symptoms or adverse effects.
You have successfully identified the underlying cause of illness in the Williams family water
contamination case. Now you are presented with a new case and a new challenge. You will
investigate the relationship between exposure and illness in another cluster of patients as you
analyze patient risk factors and medical test results. You will then design an experiment to test the
effects of a particular chemical and doses of that chemical on plant growth. You will use your
results to produce a dose-response curve and relate this graph to overall effect of the selected
Computer with Internet access and Microsoft Excel
Laboratory Journal
Project 4.1.4 Case Report
Biomedical Sciences Experimental Design resource sheet
Safety glasses
50mL of a test chemical
Permanent marker
Masking tape
Beakers (various sizes)
Graduated cylinders
Disposable transfer pipets
Distilled water
Resealable plastic sandwich bags
Paper napkins
Radish seeds
Additional laboratory equipment (as needed)
© 2011 Project Lead The Way, Inc.
BI Project 4.1.4 Dose Response – Page 1
Part I: Pinpointing the Poison
1. Obtain a copy of the Project 4.1.4 Case Report and read the case background as well as the
toxicological findings.
2. Note that the individuals have suspected exposure to lead. Research lead poisoning and
devise a scenario that explains the toxicology results. Compile your ideas into one succinct
summary that addresses the questions listed below. Use the questions as a guide. You do not
need to answer the questions in a numbered list. Add this summary to the heading Case
Summary on your case report and maintain a copy in your Mission File.
o What is the most likely source of the lead?
o How are individuals in the house exposed? What are the most likely routes of
o What actions put each person at increased (or decreased) risk for lead poisoning?
o Why do some individuals test positive for lead but show few to no symptoms?
o What are some factors that influence who gets sick?
o What is the most common treatment plan for patients with lead poisoning? How can
these patients be helped? What follow-up is necessary for the patients and the home?
3. Answer Conclusion question 1.
4. Research the short-term and long-term effects of lead poisoning. How does lead affect the
body systems or process listed below? Your teacher will assign you and a partner one of the
systems below.
Effects of Lead on This System or Process
Reproductive System
Skeletal System
Endocrine System
Nervous System Adult
Nervous System Child
Blood Composition
© 2011 Project Lead The Way, Inc.
BI Project 4.1.4 Dose Response – Page 2
5. Share your findings with the class. Fill in your chart with information presented by your
6. Answer Conclusion questions 2 and 3.
Part II: Seed Toxicity Testing
In Part I, you learned that varying doses of a chemical can have different effects on an individual.
Toxicologists study data from populations that have been exposed to specific toxins to determine the
overall effect on the body. In this part of the activity, you are playing the role of a toxicologist exploring
the effect a chemical has on an organism, the radish plant. Dose is the amount of exposure to an
agent, a measure of how much of the particular chemical is taken into the body. Response is the
body’s reaction to this dose.
7. Brainstorm how you can determine if a particular chemical at different doses is harmful or
beneficial to a living organism. Discuss your ideas with a partner and then with the class.
8. Take notes as your teacher presents the Dose Response Relationships presentation.
9. Obtain a Biomedical Sciences Experimental Design resource sheet from your teacher or your
Mission File.
10. Note that in this experiment, you will be using plants as your living organism. Choose a
chemical for testing from the list below:
Liquid detergent
Insect repellant
Artificial sweetener
Fruit punch
Window cleaner
Instant coffee
Other chemical as approved by your teacher
11. Design an experiment to test the effect of varying concentrations of your selected chemical on
the growth of radish seedlings. Using the Experimental Design resource sheet as a guide,
record a complete plan for your experiment in your laboratory journal. Your experiment must
adhere to the following parameters:
o Begin with 50mL of your test chemical. If your chemical is solid, make a solution of the
chemical by mixing it with water. Follow the directions on the package to make 50ml of
the solution. If no directions are available, make the solution as saturated as possible.
o Prepare 20mL of a control sample as well as 5 other samples at the following percent
concentrations of the chemical – 6.25%, 12.5%, 25%, 50%, and 100%. Use the formula
below to help you prepare these solutions. Record all calculations in your laboratory
𝑃𝑒𝑟𝑐𝑒𝑛𝑡 𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 =
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑐ℎ𝑒𝑚𝑖𝑐𝑎𝑙
× 100
𝑇𝑜𝑡𝑎𝑙 𝑣𝑜𝑙𝑢𝑚𝑒
© 2011 Project Lead The Way, Inc.
BI Project 4.1.4 Dose Response – Page 3
o Use radish seeds as your model organism. As a plant begins to grow, a root tip pushes
through the eye of the seed. Look for the appearance of roots to signal germination.
o Grow your plants on napkins or paper towels placed in sandwich bags. Make sure to
choose a set number of seeds and allow sufficient space between each plant. Refer to
your teacher for a space to place your experiment once you have assembled all
o Control for all other variables in your experiment and clearly label all samples.
o Observe and compile data for 3 days.
o Report qualitative findings (anything you observe) as well as quantitative findings (i.e.,
number of seeds that have germinated/have not germinated). Design a data table in
your laboratory journal that organizes your data.
12. Share your experimental design with your teacher, including your calculations for your
solutions and your desired equipment and glassware.
13. Prepare your solutions and set up your experiment. Store your samples in a space designated
by your teacher.
14. Record all findings in the data table in your laboratory journal.
Part III: Graphing Dose-Response
Scientists graph data to help them understand the relationship between dose and response. The
dose the seeds received is related to the concentration of chemicals in each experimental set-up.
15. Review your notes from the Dose-Response Relationships presentation.
16. Observe the two dose response curves (A and B) shown below. In your laboratory journal,
describe how the two graphs differ. What do they tell you about dose and response, in each
© 2011 Project Lead The Way, Inc.
BI Project 4.1.4 Dose Response – Page 4
17. Analyze your growth results from Part II and make any final notes to your data table.
18. Use Microsoft Excel or graph paper to graph the data that you have recorded for Day 3 of your
seed investigation. The dose is recorded on the x-axis and the response is recorded on the yaxis. For this experiment, the response you should graph is lack of germination. Plot the
number of seeds that did not germinate at each concentration.
19. Obtain data from two additional groups.
20. Graph this data on the same graph you created in Step 14. Clearly label the chemical related
to each line on your graph.
21. Include the graph in your laboratory journal.
22. Analyze your graph and write down any conclusions you can make from the curves you have
graphed. Compare results for the three chemicals.
23. If possible, determine a threshold value for your chemical. Is there a safe dose of your
chemical before you see adverse results? If not, describe an additional experiment that could
help you determine a threshold dose.
1. What factors influence when and if a person experiences symptoms from a particular
2. Because of similar chemical properties, the body confuses lead with calcium. Given what you
know about the role of calcium in the body, explain why this can be detrimental to human body
3. Given what you know about the effects of lead on the body systems, why is lead poisoning
prevention taken so seriously, especially in relation to young children?
4. Describe precautions a person could take to avoid inhaled toxins.
5. Explain why the whole population of seeds in one bag may not have responded to the dose in
the same manner.
6. What were the overall effects of your tested chemical on plant growth? How would you classify
your chemical? Harmful, beneficial, or neither? Explain.
7. Explain why the results of your experiment most likely cannot be applied to human response.
8. Why do think medications such as Tylenol suggest a specific dose for infants, children, and
© 2011 Project Lead The Way, Inc.
BI Project 4.1.4 Dose Response – Page 5