Porphyrins Flashcards
Porphyrins
- heterocyclic macrocycles
- composed of four modified pyrrole subunits interconnected at their α carbon via methine bridges (=CH-)
- aromatic
- they obey Huckel´s rule for aromaticity
What is the most abundant porphyrin in the human body called?
heme
What is heme?
- the pigment in red blood cells
- a cofactor of the protein hemoglobin
What is the parent porphyrin called?
porphine
What is the substituted porphines called?
pophyrin
What is heme?
the prosthetic group of proteins called homoproteins.
Homoproteins
- hemoglobin
- myoglobin
- cytochromes
- catalase
- peroxidase
Homoproteins facts
they are rapidly synthesized and degraded
What is the synthesis and degradations of porphyrins an important part of?
synthesis and degradation of porphyrins is an important part in the nitrogen balance
What does porphyrin consist of?
porphyrin consist of four pyrrole rings, A, B, C, and D interconnected by methine bridges (=CH-), and different lateral substituents (O)
What is the precursor of porphyrin called?
porphyrogens
What color is porphyrin?
- purple (?)
- colorful
What is the most abundant derivative of porphyrin?
porphyrin IX - i.e. heme
What varieties of heme do we have?
- A
- B
- C
Heme A
- found in cytochrome a+a3
- differs from heme B and C by side substituents
Heme C
- acts in cytochrome C, where it binds to the atom residues His 18 and Met80
- vinyl groups of heme C forms covalent bonds with -SH residues of Cys14 and Cys 17 of the enzyme protein
Ion Fe2+/Fe3+ forming a part of Heme B of cytochrome b
- is not able to bond with O2 or with H2O
- participates in the transport of electrons through respiratory chain only
Heme B
- creates two additional coordination bonds with a water molecule and O2 and the nitrogen atom og His being the part of globin
- in this way the heme of hemoglobin or myoglobin can alternatively attach and detach the molecule of oxygen
Chlorophyl
- a green pigment found in almost all plants, algae, and cyanobacteria
- allows plants to obtain energy from lights
What does the pophyrins rings of chlorophyl contain?
Mg2+ ion
Chlorophyl a:
contains unsaturated alcohol -pythol- bounded at position 7 by ester bond
Chlorophyl b:
differs from “chlorophyl a” by formyl group at position 3
Chlorophyl c:
does not contain phytol, and at the position 4, instead of ethyl group, propanate is connected
Chlorophyl d
instead vinyl group at the 2 position, contains formyl group
Where does synthesis of heme occur?
in the bone marrow precursor´s red blood cells and in the liver
