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Cancer Warrior

Classroom Activity

To determine the toxicity of salt to an intracellular liver process using a dose response curve.

Materials for each team
  • copy of "What's the Right Dose?" student handout (HTML)
  • dropper bottle of .17 fluid ounce (5 ml) of liver cell homogenate
  • dropper bottle of .17 fluid ounce (5 ml) of 2 percent salt solution
  • test tube and test tube rack spot plate balloons
  • watch showing seconds plastic pipette
  • graduated cylinder (.34-.85 fluid ounces; 10-25 ml)
  • 1.0-1.35 fluid ounces (30-40 ml) of 3 percent hydrogen peroxide
  • safety glasses
  1. Gather the materials listed above and in Materials Preparation below.

  2. Organize students into teams of two and provide each team with a copy of What's the Right Dose? activity page and a set of materials.

  3. Explain to students that they will be determining how different salt concentrations affect the liver's ability to break down toxic hydrogen peroxide.

  4. Students will conduct the experiment three times. Discuss with them why it is important to conduct more than one trial at each dose and report the average. Remind students to note sources of error as they conduct each trial. Assign one group to do the experiment as the control group, i.e., the liver cells that get no dosages of salt.

  5. Assign each team a number of drops to experiment with, from 0 (control group) to 12. Have students begin, allowing a full four minutes for the salt to "act" upon the liver cells. When they are ready, students can start their three trials using the instructions on the student activity page.

  6. Once students have recorded their results, have them determine the average of the three trials. Include each team's average on a class data table indicating: Team, Dosage of Salt (# of drops), and Average Response Time (# of seconds).

  7. Have students graph the data by putting Dosage of Salt (# of drops) on the X-axis and Degree of Inhibition (# of seconds) on the Y-axis. You can establish degree of inhibition values together as a class or use the Sample Test Results values in the Activity Answer.

  8. To complete the lesson, discuss with students the four phases of clinical trials (see Activity Answer for more information).

Materials Preparation
Liver cell homogenate: Blend 1/4 pound (113.4 g) of fresh beef liver with 13.5 fluid ounces (400 ml) of water in a blender. If possible, strain homogenate through a cheese cloth. Keep in refrigerator until 20 minutes prior to use. Put into dropper bottles for each team.

2 percent salt solution: Add .07 ounces (2 g) of table salt to 6.8 fluid ounces (200 ml) of tap water. This will yield an approximately 2 percent salt solution. Put into dropper bottles for each team.

3 percent hydrogen peroxide solution: This can be purchased in any pharmacy. Do not use a higher percent hydrogen peroxide solution. Make sure you check the expiration date. Provide 1.7 fluid ounces (50 ml) available to each team.

Balloons: Choosing the right size is critical. If too small, the balloons will fill up too fast; if too big, they will fill up too slowly.

Activity Answer

Clinical trials are used to determine the efficacy and safety of new drugs or treatments. According to National Institutes of Health, there are four phases in clinical trials:

Phase I: The drug is tested on humans for first time, usually on between 20 and 80 people. Researchers begin to evaluate the drug's overall safety, its safe dosage range, and any side effects it produces.

Phase II: In this phase, the drug is further evaluated with testing on a larger group of people (100 to 300).

Phase III: The drug is administered to large groups of people (1,000 to 3,000) to confirm its effectiveness, monitor its side effects, and compare it to commonly used treatments.

Phase IV: After the drug has been marketed, testing is continued to monitor how the drug reacts in various populations and determine the consequences of long-term use.

This activity models part of a Phase I clinical trial—investigating safe dosages. Students plot and use a dose response curve to determine the toxicity of salt on an intracellular liver process. The role of healthy liver cells is to deactivate and eliminate a wide variety of toxic molecules in the body, including hydrogen peroxide—H2O2—which can damage cells and tissues. Since hydrogen peroxide is broken down into two harmless substances, water and oxygen, the rate at which oxygen gas is produced can reveal whether liver cells are functioning normally. Salt inhibits the ability of liver cells to change hydrogen peroxide into water and oxygen.

Breaking down hydrogen peroxide into water and oxygen is a two-step process. During this process, free radicals are formed, which have the ability to create havoc within the cell. If the liver is unable to deactivate and eliminate hydrogen peroxide, cells and body tissues may be harmed or poisoned, and thus be unable to carry out their vital cell processes.

Sample Test Results

Links and Books


Cooke, Robert. Dr. Folkman's War: Angiogenesis and the Struggle to Defeat Cancer. New York: Random House, 2001.
Provides an account of Folkman's work on angiogenesis, offering readers insight into how medical research is conducted.


Folkman, Judah. Fighting Cancer by Attacking Its Blood Supply.
Explains how angiogenesis provides one of the keys to tumor growth, and how anti-angiogenic drugs could be successful in stopping cancer from proliferating, perhaps in combination with traditional cancer treatments.

Web Sites

NOVA Online—Cancer Warrior
Provides program-related articles, interviews, interactive activities, resources, and more.

Includes information about clinical trials and features a section to help users locate ongoing trials. A service of the National Cancer Institute.
Provides a primer on understanding clinical trials, as well as searchable information about current clinical research studies being conducted.

Understanding Angiogenesis
Briefly explains key concepts in tumor angiogenesis, such as metastasis and angiogenesis inhibitors. Includes illustrations.


The "What's the Right Dose?" activity aligns with the following National Science Education Standards.

Grades 5-8

Science Standard A:
Science as Inquiry

Abilities necessary to do scientific inquiry

Life Science

Science Standard C:
Life Science

Structure and function in living systems

Grades 9-12

Science Standard A:
Science as Inquiry

Abilities necessary to do scientific inquiry

Life Science

Science Standard C:
Life Science

The cell

Teacher's Guide
Cancer Warrior

Video is not required for this activity