General Chemistry

Oxygen-Carrying Protein in the Blood: Hemoglobin

Hemoglobin is the protein that transports oxygen (O2) in human blood from the lungs to the tissues of the body. Proteins are formed by the linking of amino acids into polypeptide chains. An individual amino acid in a protein is known as a "residue." The arrangement and interactions of the amino-acid residues within the protein determine the protein's shape and contribute substantially to its function. Hemoglobin is a globular protein (i.e., folded into a compact, nearly spherical shape) and consists of four subunits, as shown in Figure 2. Each protein subunit is an individual molecule that joins to its neighboring subunits through intermolecular interactions. (These subunits are also known as peptide chains. You will learn more about the nature of amino acids and peptide subunits in the tutorial entitled, "Iron Use and Storage in the Body: Ferritin and Molecular Representations".)


Figure 2

This is a molecular model of hemoglobin with the subunits displayed in the ribbon representation. A ribbon representation traces the backbone atoms of a protein and is often used to represent its three-dimensional structure. The four heme groups are displayed in the ball-and-stick representation.

Note: The coordinates for the hemoglobin protein (in this and subsequent molecular representations of all or part of the protein) were determined using x-ray crystallography, and the image was rendered using SwissPDB Viewer and POV-Ray (see References).

View this molecule interactively

Note: To view the molecule interactively, please use Jmol, and click on the button to the left.

To understand the oxygen-binding properties of hemoglobin, we will focus briefly on the structure of the protein and the metal complexes embedded in it.


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This page created by Matt Traverso, Washington University in St Louis.
© 2004, Washington University.
Materials and Information present may be reproduced for educational purposes only.

Revised: 2004-08-08