Biological Compounds

= Mg

= C

= O

= H

= N

chlorophyll a
One of the green pigments in plants. Plants appear green because chlorophyll a absorbs red and purple light; the reflected light consequently appears green. Note the square planar structure around the Mg atom.

= Fe

= C

= O

= H

= N

heme
Heme is the iron-containing complex in hemoglobin. In hemoglobin, the red heme complex is bonded to a large protein molecule (globin) by coordination of the protein to a position above the plane of the heme molecule. Note the square planar structure around the Fe atom.

= Co

= C

= O

= H

= N

= P

vitamin B ₁₂
Vitamin B ₁₂ is one of the essential vitamins required for living organisms. Note the octahedral structure around the Co atom.