Heme Group
The iron-containing molecular structure at the core of hemoglobin that reversibly binds oxygen, enabling red blood cells to transport it from lungs to tissues.
A ring-shaped molecular structure containing an iron atom at its center, found in hemoglobin and other proteins. The iron atom can reversibly bind oxygen molecules, making heme groups essential for oxygen transport in blood. Each hemoglobin molecule contains four heme groups. Heme groups also appear in other proteins like myoglobin and cytochromes, where they facilitate oxygen storage or electron transfer.
What this means in real life
When you breathe in, the iron atoms in your red blood cells' heme groups latch onto oxygen molecules; when those cells reach your muscles or brain, the heme groups release that oxygen so your cells can use it for energy.
What it isn’t
A heme group is not the entire hemoglobin protein — it's just the small iron-containing piece embedded within hemoglobin's larger protein structure, like a jewel in a setting.
Commonly misused online
Wellness influencers sometimes conflate 'heme' with 'heme iron' from meat, implying all heme is dietary, when heme groups are actually synthesized inside your own cells and only incidentally consumed when eating animal tissue.