Difference between Protoporphyrin and Porphyrin? [closed]








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I understand that Porphyrin is defined as 4 pyrole rings linked by methenyl bridges. When this porphyrin ring is associated with a Ferrous ion (Fe 2+) we get the Heme molecule. However my book mentions that Heme is a complex of Protoporhyrin IX and Ferrous ion. So what is the difference between a Porphyrin ring and a Protoporphyrin ring?




From [here](https://www.differencebetween.com/difference-between-porphyrin-and-protoporphyrin/):



> 
> Protoporphyrin is a derivative of porphyrin. The key difference between porphyrin and protoporphyrin is that porphyrin is a group of aromatic chemicals which has four modified pyrrole subunits interconnected to each other, whereas protoporphyrin is a derivative of porphyrin which has propionic acid groups.
> 
> 
> 


Protoporphyrine contains [porphine](https://en.wikipedia.org/wiki/Porphine) as core which is the simplest of the porphyrin chain. Picture from Wikipedia:


[![enter image description here](https://i.stack.imgur.com/g6usx.png)](https://i.stack.imgur.com/g6usx.png)


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