Heme: a
coordination
complex between iron
and a large cyclic
ligand
which coordinates
thru
4 sites to
form a
coordinated
porphyrin ring.
Myoglobin: a single polypeptide chain of
153 amino acids with a
single heme unit.
Hemoglobin:
comprises 4 myoglobin type
subunits (called globin
subunits).