|MadSci Network: Anatomy|
Iron is an essential mineral for both carrying oxygen in the blood and using oxygen in cells. A single atom of iron lies at the core of Heme, a ring disk-shaped molecule which is the business end of both hemoglobin and cytochrome c. Red blood cells use hemoglobin to ferry oxygen from the lungs to the tissues, and then the mitochondria in the cells that receive the oxygen use cytochrome c in the process that converts energy and oxygen into ATP and water. There is also heme in myoglobin, a cousin of hemoglobin which is used by the muscles to store oxygen for strenuous exertion.
However, as I mentioned above, there is one atom of iron per heme group, and only one heme group per protein, which means there are many hundreds more atoms of carbon, oxygen, and nitrogen than iron (actually, hemoglobin is a complex of four subunits each with its own heme, but the total ratio of iron to other atoms is the same). Cytochrome c makes up only a tiny fraction of the protein in a cell, and myoglobin is far out numbered by the contractile proteins in muscles. Although hemoglobin makes up most of the protein in red blood cells, RBC's make up less than half of the blood. Still, about half of the body's iron is in the blood's hemoglobin.
According to the American Red Cross, one pint of blood contains about 250 milligrams of iron. Since the average human has about 10 - 12 pints of blood total, and this accounts for half of the iron in the body, that comes out to between 5 and 6 grams of iron per adult human body. That's just enough iron to make a medium- sized nail (for our non-metric audience, 5 grams is the weight of a nickel: 5 cents = 5grams). To answer the gist of your question (finally), you would need a lot of wood to build anything out of the iron collected from distilling human bodies.
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