heme

American  

[heem] / him /

noun

Biochemistry.

1. a deep-red iron-containing blood pigment, C 34 H 32 N 4 O 4 Fe, obtained from hemoglobin.

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heme Scientific  

/ hēm /

1. The deep red, nonprotein, iron-containing component of hemoglobin that carries oxygen. Heme is a porphyrin with an iron atom at its center. One of the free valence electrons of the iron atom of heme is bound to the hemoglobin molecule, while the other is available for binding to an oxygen atom. A hemoglobin molecule contains four hemes. Chemical formula: C ₃₄ H ₃₂ FeN ₄ O ₄ .

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Etymology

Origin of heme

First recorded in 1920–25; shortened form of hematin

Compare meaning

How does heme compare to similar and commonly confused words? Explore the most common comparisons:

• heme vs. hemoglobin

Example Sentences

Heme is highly toxic; bilirubin, the breakdown product in mammals, is less so.

From Science Magazine • Jun. 8, 2023

Heme, or soy leghemoglobin, is found most abundantly in animal flesh and is the catalyst for hundreds of chemical reactions that occur while a burger is cooking.

From Washington Post • Oct. 23, 2019

Heme has even greater affinity for nitric oxide than oxygen, and the body uses nitric oxide as a signaling molecule to control blood pressure.

From Scientific American • May 6, 2019

Heme iron, from animal foods such as meat, poultry, and fish, is absorbed more efficiently than non-heme iron from plant foods.

From Textbooks • Jun. 19, 2013

Marry, this is our device-     That Falstaff at that oak shall meet with us,     Disguis'd, like Heme, with huge horns on his head.

From The Merry Wives of Windsor by Shakespeare, William