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

If the crystals clump, they lose surface area needed to process more heme efficiently.

From Science Daily • Mar. 19, 2026

Other human remains found elsewhere in Herculaneum had iron oxide deposits in the skull, suggesting that the fluids in the skull were vaporized by the heat, leaving only traces of degraded heme proteins.

From Salon • Mar. 4, 2025

The company’s burgers also contain a genetically modified plant-based version of heme, an iron-containing molecule that is a component of beef.

From Los Angeles Times • May 31, 2024

Red meat also has high levels of a type of iron called heme, which researchers believe can affect insulin production.

From Seattle Times • Oct. 22, 2023

Once all the oxygen molecules have been loaded onto heme, the four leaves of hemoglobin tighten around the oxygen like a saddle clasp.

From "The Gene" by Siddhartha Mukherjee