BIOCHEMISTRY: Protein Function–Myoglobin and Hemoglobin by A. Scheider
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Alpha helix polypeptide chains
Heme complex with Oxygen attached to iron Heme complex without Oxygen attached to iron
Beta sheet polypeptide chains
Model of Hemoglobin Molecule
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Hemoglobin: quick facts
Hemoglobin is a protein that carries Oxygen and releases Oxygen to the body via the blood circulation. Hemoglobin is made of 4 polypeptide chains with each chain containing an iron-heme structure that contains the oxygen-binding site. Each hemoglobin molecule twists a polypeptide chain into a helical secondary structure. The helices drape around the heme group and form into a tertiary structure subunit. The four subunits are packed into a globular quaternary protein structure. The iron-heme structures give the red color to hemoglobin. Each hemoglobin molecule can carry and/or release a maximum of 4 oxygen molecules. The oxygen is picked up in the lungs and delivered to tissues as neede.d
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Oxygenated and Deoxygenated states of Hemoglobin (Hgb)
A molecule of hemoglobin loaded with oxygen is referred to as oxyhemoglobin. Oxyhemoglobin is an unstable protein that easily reverses its’ oxygen attachments. When a molecule of hemoglobin is empty of oxygen attachments, it is called deoxyhemoglobin. Portions of the terminal end of the amino acids in the deoxyhemoglobin will work together to form ionic pairs.
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These ionic pairs decrease the acidity of the blood by binding one hydrogen atom for every 2 oxygen molecules released. The resulting lowering of blood pH will trigger the intake of more oxygen. Deoxyhemoglobin presents in a bluish red color in the blood while oxyhemoglobin is bright red.
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(Childs, 2012)
Myoglobin vs Hemoglobin
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Heme= Fe-protoporphyrin IX C34H32FeN4O4
Both Myoglobin and Hemoglobin contain the HEME complex
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