Hemoglobin Affinity (Biology)

Hemoglobin is very crucial to our blood’s capacity for storing and transporting oxygen. As oxygen is relatively insoluble in blood plasma (.3 milliliters of oxygen per 100 milliliters of plasma), respiratory pigments such as hemoglobin and hemocyanin (arthropods and mollusks) may raise the oxygen transporting capacity of the blood as much as seventy fold. In most of the invertebrates, respiratory pigments are merely dissolved in the blood plasma, which, in contrast to vertebrates and echinoderms, use …

…up oxygen from hemoglobin. It begins to release significant amounts of this oxygen only when the P02 in skeletal muscle falls below 20 mmHg, and acts as an “emergency reserve” of oxygen. However, during normal or moderate activity, myoglobin holds onto it’s oxygen, and only during extreme activity when the partial pressure of oxygen in the muscle cells drop to zero, does myoglobin gives up its oxygen, providing one more back up reserve of oxygen.