In Your Classroom: Blood Simple

by Sharon Radford     Department: In Your Classroom

Blood. We take it for granted until we need it. In biology classes we talk about the oxygen carrying properties of hemoglobin in physiology, about inheritance of blood types in genetics, about surface antigens in immunology. Hemoglobin seems to be everywhere in our classes.

Nearly all biology textbooks have links to diagrams of hemoglobin which show the four subunits and the site of oxygen binding, but a really good tutorial that not only shows the structure of hemoglobin in several ways (space-filling, ball and stick) but also clearly shows the interaction of oxygen with the iron porphyrin embedded in the molecule can be found here.

This program on the use of perfluorocarbons as an oxygen-carrying substance goes to the heart of the role of hemoglobin, its importance in picking up oxygen and delivering it to the tissues. However, while students understand the importance of hemoglobin picking up oxygen in the lungs, I don't think they fully understand that hemoglobin needs to let go of the oxygen in the body tissues. We can underscore this aspect of hemoglobin's role when we do experiments involving cell respiration.

Theresa Holtzclaw presents a graphic and interactive overview of cell respiration and how a simple and inexpensive respirometer works at the Lab Bench site sponsored by Prentice-Hall. This is the method I use with my classes. On this web site, students can observe the set-up and the sample experiment before setting up their own.

For a more high-tech version, or for more advanced classes, check out Robert Goodman's "Cell respiration: A computer based laboratory" at the Access Excellence Activities Exchange site.

This set of experiments uses the fact that carbon dioxide lowers the pH of a solution, and thus changes the color of an indicator as respiration proceeds. In addition, several companies offer oxygen and carbon dioxide probes which can be used to measure respiration directly.

To get down to the level where the exchange happens, I like to set up a demonstration in which students can see blood flow for themselves in the capillaries in the thin tissue of a the tail of a fish. If you have an aquarium in your classroom, take one of the fish and use a wet cotton ball to keep the gills moist. I use a paper towel to hold the cotton in place and to keep the fish relatively immobile. Lay the fish on a microscope slide and focus on the tail. Usually, we see small blood vessels of various sizes, including the small capillaries where the blood cells are moving slowly. The fish may have to be repositioned several times, and I usually allow five or ten minutes before returning the fish to the aquarium.

Finally, to get back to perfluorocarbons as a substitute for hemoglobin, the following article presents an anesthesiologists view of the subject:

Leone, Bruce J., M.D. "Artificial Blood: What Is It? Will I Use It?" Jacksonville Medicine, December, 1998.

Dr. Leone is an associate professor of anesthesiologist at the Mayo clinic in Jacksonville, Florida. His article covers the history of blood substitutes, the physiology of oxygen transport, and the pros and cons of perfluorocarbons.

Additional WIRED Science Video Segments
Don't forget to check out our Video Section for other segments from WIRED Science that you can use in your classroom.

Tags: biology, blood, classroom, hemoglobin, resources, respirometer, student, video, wired science

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