► Oxygen is reversibly bound to hemoglobin in red blood cells. Each molecule of hemoglobin can carry a maximum of four molecules of O2. Because of positive cooperativity, the affinity of hemoglobin for O2 depends on the Po2 to which the hemoglobin is exposed. Therefore, hemoglobin picks up O2 as it flows through respiratory exchange structures and gives up o2 in metabolically active tissues. Review Figure 48.12
► Myoglobin has a high affinity for O2 and serves as an O2 reserve in muscle.
► There is more than one type of hemoglobin. Fetal hemoglobin has a higher affinity for O2 than does maternal hemoglobin, allowing fetal blood to pick up O2 from the maternal blood in the placenta. Review Figure 48.13
► The affinity of hemoglobin for O2 is decreased by the presence of hydrogen ions or 2,3 bisphosphoglyceric acid.
► Carbon dioxide is transported in the blood principally as bicarbonate ions. Review Figure 48.14
See Web/CD Activity 48.2
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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.