Explanation:
1. By itself, heme is not a good oxygen carrier. It must be part of a larger protein to prevent oxidation of the iron.
3. Heme is composed of an organic protoporphyrin component and a metal atom.
4. Each hemoglobin molecule can bind four oxygen molecules; each myoglobin can bind only one oxygen molecule.
6. Both hemoglobin and myoglobin contain a prosthetic group called heme, which contains a central iron atom.
7. Each iron atom can form six coordination bonds: One of these bonds is formed between iron and oxygen.
Hemoglobin is an oxygen binding protein comprising four peptide subunits: two α subunits and two β subunits. The precursor to the heme group, protoporphyrin joins to Iron in the form Fe to form heme, present in both myoglobin and hemoglobin. The iron coordinately bonds, by giving up electrons- four of these are bound in the Fe-protoporphyrin bond, while one is attached to the histidine residue of the protein. This only leaves one coordinate site left with which the Fe can bind to an oxygen molecule.
Further explanation:
The equilibrium between oxyhemoglobin (haemoglobin in its oxygen bound state and hemoglobin (free of oxygen molecules). Each molecule of hemoglobin has the ability to bind up to four oxygen molecules at a time; this occurs via cooperative binding- meaning that with increased hemoglobin- oxygen binding at the protein hemoglobin’s subunits,(where oxygen is a ligand) there is an increase in its affinity for oxygen.
This is because there is a conformational change in the hemoglobin molecule due to the altered orientation of the protein’s secondary structures, making it easier for a second molecule of oxygen to successively followed by more O2-Haem binding until the molecule is saturated. However with only one Hem subunit myoglobin can only bind to one molecule of oxygen, while hemoglobin can bind four.
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