"bacteria first appear in the fossil record about 3.5 billion years ago. humans appeared in the fossil record only a few million
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Answer:
D) over 90
Explanation:
As we know, hemoglobin is the protein found in red blood cells that is in charge of oxygen transportation, and the relation between the percentage of oxygen that binds to hemoglobin and the partial pressure of oxygen in the blood can be represented through the oxygen - hemoglobin dissociation curve, as shown in the attached image.
As we can see in the image, the curve has a sigmoid shape, and this is due to the allosteric interactions between the subunits of the hemoglobin, which change their conformation with each oxygen molecule that binds in order to increase even more the oxgen affinity. This curve is constantly shifting to the right and to the left depending on the conditions of the blood, like temperature, pH, partial pressure of carbon dioxide and the concentration of diphosphoglycerate (DPG).
When the PO2 is around 70 mmHg, as we can see in the curve, the hemoglobin is saturated around 90% or more, reaching a plateu in the curve where the oxygen is not binding as fast anymore, because there are almost no more free binding sites left in the hemoglobin molecule.
