What is heme?
Heme is a combination of a protoporphyrin ring and an iron (Fe) atom. The protoporphyrin ring is essentially an outer ring of 20 carbon atoms and an inner ring of 4 nitrogen atoms. Various side chains are attached in different forms of heme. The Fe atom is bound in the center by the 4 nitrogen atoms. 2. Name three roles of heme in proteins A: In hemoglobin, there are four heme groups each of which transports one molecule of oxygen to tissue (in myoglobin, there is only one heme). In catalase, the Fe atom of the heme is the active site for breakdown of hydrogen peroxide. In cytochromes, heme is often involved in electron transfer reactions by cycling between a reduced and oxidized state. 3. What is methemoglobin and how is it formed? A: It is hemoglobin with an oxidized heme. When oxidized, the Fe atom is in the 3+ state (ferric). Normally heme is ferrous (2+). Methemoglobin cannot bind oxygen. However, it binds cyanide (CN) strongly in cyanide poisoning, preventing cyanide from blockin
Related Questions
- It has been suggested that humans have intestinal receptor(s) for haem (heme) iron which can only be found in animal flesh. Doesn this mean we are biologically adapted to eating meat?
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