Eating green vegetables is a very important part of staying healthy. Chlorophyll is the pigment in vegetables that makes them green and it is involved in transforming the sun's energy to energy that we can use for food. We would be in sad shape if chlorophyll did not exist. Hemoglobin is the molecule in our red blood cells that is responsible for binding oxygen and transferring it to our tissues. Without hemoglobin we would be in equally sad shape, we are fortunate that both molecules exist. In an effort to emphasize the importance of eating green foods, I frequently hear lecturers claim that the only difference between chlorophyll and hemoglobin is that chlorophyll has magnesium and hemoglobin has iron. That makes a great story but it is simply not true. While both molecules share a porphin ring (see below), that is where the similarities end. So, if you hear someone make this claim, realize that they have not done their homework and looked more carefully at the chemical structures of the two molecules. This doesn't make eating green vegetables any less important, but it does call into question the accuracy of lecturers making such claims.