the.com/hemoglobin
the four-armed iron taxi that hauls oxygen and gives blood its bragging-rights red
oxygen capacityone molecule carries four oxygen passengers at once
color trickred oxygenated, dark blue-purple when spent
daily outputbody builds millions of red cells per second
carbon monoxidebinds it 200 times tighter than oxygen
ancient cousinplant root nodules carry a green relative, leghemoglobin