Hi! I’m hemoglobin.
I live inside red blood cells and eat all the iron in the fridge. I’m very attractive (see my photo attached). My shape changes as the number of oxygen molecules attached to me changes. The more oxygen molecules bound to me, the more attractive I become to oxygen, and the more oxygen wants to bind to me. When only one oxygen molecule is bound to me, I’m not so attractive. But when 3 oxygen molecules are bound to me, the fourth one can’t bind itself fast enough, so beautiful I become. (When I have 4 oxygen molecules attached, I can’t stop looking at myself in the mirror.) This change in my affinity for oxygen is important because it facilitates the loading of oxygen in lungs and unloading of oxygen in the muscles and other organs.
This change in my shape is how doctors and nurses know when blood’s oxygen saturation is low. You know that little finger clip they put on your finger in the hospital or doctor’s office? There’s an infrared light inside of that clip. When I change shape, I change how I refract light. So, that clip is “reading” how the infrared light is refracting because of my shape. If blood’s oxygen saturation is less than optimal (98-100% at sea-level), the light refracts differently because my shape is different. Pretty cool, huh?
How saturated I am with oxygen is determined by the partial pressure of oxygen in blood. The lower oxygen’s partial pressure, the lower my saturation. When you go skiing, hiking, or running at high altitude, the partial pressure of oxygen in the air decreases, which decreases the partial pressure of oxygen in your blood. Up to an altitude of about 3,000 feet, the drop in the air’s partial pressure of oxygen is minimal, so my saturation doesn’t change; it remains at 98-100%. But when you travel above 3,000 feet, my saturation begins to drop. That’s why it’s harder to do aerobic exercise at high altitude—because I have less oxygen bound to me as I travel through your circulatory system.
Now, tell me how beautiful of a protein I am. Want to learn more about me?