In this higher energy state, this electron is more readily transferred to another molecule. This starts a chain of electron-transfer steps, which ends with an electron transferred to carbon dioxide. Meanwhile, the chlorophyll which gave up an electron can accept an electron from another molecule. This is the end of a process which starts with the removal of an electron from water. Thus, chlorophyll is at the center of the photosynthetic oxidation-reduction reaction between carbon dioxide and water.
Heme is bright red.
In the red blood cells of vertebrates, heme is bound to proteins forming hemoglobin. Hemoglobin combineswith oxygen in the lungs, gills, or other respiratory surfaces and releases it in the tissues. Another relative of chlorophyll is vitamin B 12 . Vitamin B 12 contains a cobalt ion at the center of the porphyrin. Like heme, vitamin B 12 is bright red.