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  Home > JCE Print > Journal of Chemical Education > Issues > 2001  > June  >
In the Classroom
Applications and Analogies
The Oxygen Dissociation Curve of Hemoglobin: Bridging the Gap between Biochemistry and Physiology
Julian Gómez-Cambronero
Department of Physiology and Biophysics, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH 45435
Cover
June 2001
Vol. 78 No. 6
p. 757
Abstract
Cooperativity is a very difficult concept for biochemistry students in the health sciences. An analogy between breaking salt bonds and tearing apart a block of four stamps has been proposed for hemoglobin (Hb). However, since tearing is equated to binding of molecules, two intrinsically contradictory terms, students still have difficulty. I apply the pictorial analogy to the releasing of oxygen instead of the binding, thus bridging biochemistry (cooperativity) with physiology (oxygen dissociation). I embark on an imaginary journey from the lungs (saturation at 100 mmHg) to the oxygen-starved tissues. The stamps represent fully loaded Hb. By making two cuts the first "oxygen" is released. For the second, only one cut is needed. With one final cut, the last two stamps are separated. This means that less energy is needed to unload oxygen: just small drops in partial pressure do the trick in the right place (tissues) but not in the wrong one (lungs). In doing this, I use the three main models of learning: association, discovery and mentoring. Additionally, by guiding students to discover the truth by themselves, I can use hemoglobin as a wonderful excuse to apply the "Socratic method" in the classroom.
More Information
*  Citation
 Gómez-Cambronero, Julian. J. Chem. Educ. 2001 78 757.
*  Keywords
 Biochemistry; Kinetics; Proteins / Peptides; Teaching / Learning Aids
*  History
 Created:
Last Updated:		 May 8, 2001
April 14, 2005
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