| MadSci Network: Other |
Interesting question, Maria. The answer is "yes, but no." Blood is red because of hemoglobin in the red blood cells. Hemoglobin is the protein that carries oxygen and carbon dioxide, and red cells are full of this protein. The oxygen and CO2 bind to iron atoms that sit in a special structure inside the protein called the "heme" group. There are only four iron atoms per hemoglobin molecule, but hemoglobin is red because of the heme groups. With oxygen bound, the color is very bright red, and with carbon dioxide, the color is very dark red. Proteins in the blood cells stick to things and stain them red. If you oxidize the stains with peroxide or bleach, the red stains disappear because the proteins break down and are dissolved away. If the stains were due to iron, like rust stains, they wouldn't be cleaned away by bleach or other oxidizers because the rust is already oxidized. So it's really the protein, hemoglobin, that causes the red stains, but this red color is in turn due to the presence of both iron and oxygen in the heme group. Paul Odgren, Ph.D. Cell Biology Univ. of Massachusetts Medical School Worcester
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