Favorite proteins of the test-writers, myoglobin and hemoglobin are oxygen carrying proteins in vertebrate organisms. Hemoglobin is the oxygen carrier in the blood. Hemoglobin also plays an important roll in carbon dioxide and hydrogen ion transport. Myoglobin helps to maintain a reserve supply of oxygen in the muscles. Hemoglobin is an allosteric protein in which the binding of O2 is controlled by H+, phosphate, and CO2 levels. Hemoglobin consists of four polypeptide chains connected by noncovalent forces (van der Waals, dipole-dipole, hydrogen bonding, and salt bridges). Each chain contains a nested heme group, in which iron forms a coordination complex in the center of the protoporphyrin ring, forming four bonds, leaving two additional coordination positions (one for a histidine side chain and one for oxygen). Hemoglobin is an allosteric protein, the binding of a molecule to one site on the protein leads to conformational changes that affect a distant site on the protein. O2 binding is cooperative (the first binding enhances additional binding by the other heme groups nested in the other polypeptide chains. Additionally, the binding of H+ or CO2 allosterically alters the binding of O2. The cooperative binding of oxygen by hemoglobin enables it to deliver much more oxygen within the capillaries than if the binding sites were independent. Additionally, higher levels of CO2 and H+ in the capillaries facilitates the release of oxygen from oxyhemoglobin (Bohr effect). (Additionally, 2,3 biphosphoglycerate (BPG) plays an important roll in modulating the oxygen affinity of hemoglobin, the difference in affinity for BPG, for example, accounting for the greater affinity of fetal hemoglobin F for oxygen).












The WikiPremed MCAT Course is a comprehensive course in the undergraduate level general sciences. Undergraduate level physics, chemistry, organic chemistry and biology are presented by this course as a unified whole within a spiraling curriculum. Please read our policies on Privacy and Shipping & Returns.  Contact Us. MCAT is a registered trademark of the Association of American Medical Colleges, which does not endorse the WikiPremed Course. WikiPremed offers the customers of our publications or our teaching services no guarantees regarding eventual performance on the MCAT.


Creative Commons License
WikiPremed is a trademark of Wisebridge Learning Systems LLC. The work of WikiPremed is published under a Creative Commons Attribution NonCommercial ShareAlike License. There are elements of work here, such as a subset of the images in the archive from WikiPedia, that originated as GNU General Public License works, so take care to follow the unique stipulations of that license in printed reproductions.