The effects of 2,3-DPG are also important in the transfer of oxygen from maternal to fetal blood. In an adult, hemoglobin molecules are composed of two alpha and two beta chains as previously described, whereas fetal hemoglobin has two gamma chains in place of the beta chains (gamma chains differ from beta chains in thirty-seven of their amino acids). Normal adult hemoglobin in the mother (hemoglobin A) is able to bind to 2,3-DPG. Fetal hemoglobin, or hemoglobin F, by contrast, cannot bind to 2,3-DPG, and thus has a higher affinity for oxygen than does hemoglobin A. Since hemoglobin F can have a higher percent oxyhemoglobin than hemoglobin A at a given PO2, oxygen is transferred from the maternal to the fetal blood as these two come into close proximity in the placenta.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.