Why does blood change colors when exposed to oxygen?



  1. 0 Votes

    Hemoglobin, a protein that carries oxygen in the body, binds with oxygen and changes shape. When this absorbs, it absorbs different wavelengths of light, which causes it to change color. When blood is exposed to air, the hemoglobin absorbs even more oxygen, causing it to turn red.

  2. 0 Votes

    I just want to make sure that it’s clear that blood does change color, but only from dark red to lighter red, not from blue to red as the common myth describes. Blood is red because the hemoglobin in the blood contains iron, but there are other animals that do have blue blood like because their hemoglobin contains copper instead. Anyway, oxygenated blood does turn a bright red as described above, but its original form is a deep, dark red. The color is maintained in syringes withdrawing blood into it’s container, depleted of oxygen. The reason veins appear blue to our eyes has to do with light absorption of blood and light reflection in skin.

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