# How many metallo-ligand bonds does iron normally form with oxygen?

**URL:** <https://boards.straightdope.com/t/how-many-metallo-ligand-bonds-does-iron-normally-form-with-oxygen/318063>\
**Category:** Factual Questions\
**Created:** [August 22, 2005, 2:38am UTC](https://boards.straightdope.com/t/how-many-metallo-ligand-bonds-does-iron-normally-form-with-oxygen/318063 "2005-08-22T02:38:20Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\
**Post date:** [August 22, 2005, 2:38am UTC](https://boards.straightdope.com/t/how-many-metallo-ligand-bonds-does-iron-normally-form-with-oxygen/318063/1 "2005-08-22T02:38:20Z")

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Is it 6? I would assume it is six, but have no idea.

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**Author:** ![chaoticbear](https://avatars.discourse-cdn.com/v4/letter/c/f07891/32.png) [@chaoticbear](https://boards.straightdope.com/u/chaoticbear)\
**Post date:** [August 22, 2005, 5:34am UTC](https://boards.straightdope.com/t/how-many-metallo-ligand-bonds-does-iron-normally-form-with-oxygen/318063/2 "2005-08-22T05:34:50Z")

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All of my biology classes are failing me. I thought that it was 2, at least in the case of hemoglobin.

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**Author:** ![Waterman](https://avatars.discourse-cdn.com/v4/letter/w/b2d939/32.png) [@Waterman](https://boards.straightdope.com/u/Waterman)\
**Post date:** [August 22, 2005, 6:47am UTC](https://boards.straightdope.com/t/how-many-metallo-ligand-bonds-does-iron-normally-form-with-oxygen/318063/3 "2005-08-22T06:47:54Z")

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Lehninger’s _Principles of Biochemistry_ states that the iron is in the +2 (Ferrous) state as stated by **chaoticdonkey**. Also, according to Lehninger, hemoglobin has a quaternary structure of four alpha-beta (sorry don’t know how to add Greek letter symbols to postings) protein subunits.

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**Author:** ![chaoticbear](https://avatars.discourse-cdn.com/v4/letter/c/f07891/32.png) [@chaoticbear](https://boards.straightdope.com/u/chaoticbear)\
**Post date:** [August 22, 2005, 4:38pm UTC](https://boards.straightdope.com/t/how-many-metallo-ligand-bonds-does-iron-normally-form-with-oxygen/318063/4 "2005-08-22T16:38:30Z")

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> [@Waterman](#):
>
> hemoglobin has a quaternary structure of four alpha-beta (sorry don’t know how to add Greek letter symbols to postings) protein subunits.

Well DUH! I could have told you that. 😛