Question

What substance gives human blood its distinctive colour?

Answer 1

Each hemoglobin protein is made up subunits called hemes which are what give blood its blood its red colour.

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Answer 2

Red Blood corpuscles contain hemoglobin and this is the reason blood looks of red color. Each hemoglobin protein is built with several subunits called hemes, which stands responsible for its red color.

More precisely, the hemes can integrate iron molecules, and these iron molecules can bind oxygen. The blood cells are of red color because of the communication between iron and oxygen.