MadSci Network: Other

Re: does blood stain clothes because of iron?

Date: Mon Aug 11 12:26:41 2003
Posted By: Paul Odgren, Assistant Professor, Dept. of Cell Biology
Area of science: Other
ID: 1060420420.Ot

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

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