Linear tetrapyrroles (called
bilanes) include: • Heme breakdown products (e.g.,
bilirubin,
biliverdin) •
Phycobilins (found in
cyanobacteria) •
Luciferins as found in
dinoflagellates and
euphausiid shrimps (krill) File:Bilirubin ZZ.png|
Bilirubin File:Biliverdin3.svg|
Biliverdin File:Phycoerythrobilin.svg|
Phycoerythrobilin File:Luciferin dinoflagellate.svg|
Dinoflagellate (R=H) and
krill (R=OH)
luciferin File:Uroporphyrinogen III skeletal.svg|
uroporphyrinogen III, an authentic tetrapyrrole Cyclic tetrapyrroles having four one-carbon bridges include: •
Porphin, the simplest tetrapyrrole •
Porphyrins, including
heme, the core of hemoglobin •
Chlorins, including those at the core of chlorophyll. Cyclic tetrapyrroles having three one-carbon bridges and one direct bond between the pyrroles include: •
Corrins, including the cores of
cobalamins, when complexed with a
cobalt ion. File:Heme.svg|
Heme group of hemoglobin with a
porphin macrocycle. File:C-3 position Chlorophyll a.svg|The
chlorin section of the
chlorophyll a molecule. The green box shows a
group that varies between
chlorophyll types. File:Cobalamin.svg|
Cobalamin structure includes a
corrin macrocycle. The tetrapyrrole portions of the molecules typically act as
chromophores because of a high degree of
conjugation in them. Therefore, these compounds are commonly colored. ==References==