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• Chlorophyll is a green color pigment in green plants and algae.• It is a magnesium- porphyrin complex.• It is a square planar complex with Mg2+ the center .• The magnesium is at the centre of the modified ring septeon (corrin).• The modified porphyrin acts as the ligand.• It is a naturally occurring chelate complex of Mg.
• Blood contains red blood corpuscles or cells .• About 95% of the dry weight of the red blood cells is composed of hemoglobin ( or haemoglobin)• 100mL of the blood of a normal male contains approximately 15g of hemoglobin all of which is within the red blood cells.• Haemoglobin contains about 0.35% of iron and thus there are 50mg of Fe per 100mL blood and 2.5g of iron in the total blood volume of 5000ml in an adult man.
• Haemoglobin is a conjugated protein having molecular weight of 64,500.• It is a tetramer in and contains four identical units which are arranged roughly in a tetrahedron .• Each unit contains FOUR identical heme groups.• Each hemoglobin molecule has four heme groups bound to the globin (a protein) on its surface.• Fe(II) in hemoglobin is in the high spin state (Fe2+ = 3d6 =t42g e2g)• Thus Fe (II) has four unpaired electrons in hemeglobin molecule.
• The structure of haemoglobin is an octahedral complex of Fe(II).• The centre of haemoglobin is occupied by Fe(II) and the four corners of the square base are occupied by the four N- atoms of the heme group.• One axial position is occupied by N- atom of histidine while the other axial positions is occupied by the H2O molecule.
Role of hemoglobin in biological living systems
• Hemoglobin is very sensitive to O2 and hence readily combines with it• Thus when we breathe in oxygen, hemoglobin (Hb) present in our body combines reversibly with the oxygen in the lungs to form oxy-hemoglobin (HbO2 )Haemoglobin + O2 ↔ Oxy- hemoglobin + H2 O(or) Hb + O2 ↔ HbO2 + H2 O
• The formation of HbO2, is called oxy- genation of hemoglobin.• In HbO2, Fe is in +3 oxidation state.• In the formation of HbO2, H2o molecules present at one of the axial positions in hemoglobin are reversibly replaced by O2 molecules.• As the blood runs through the arteries to the tissues, the oxygen pressure decreases and oxygen gets bound with the hemoglobin is set free.
• This free oxygen diffuses into the body cells where it combines with glucose(food) and oxidizes it into Carbon di oxide and water.• Thus oxygen is used in the combustion of food. C6H12O6 + 6O2 → 6CO2 + 6H20 + 38 ATP (energy)
• The oxidation of glucose to carbon di oxide is an energy releasing process in which energy in the form of ATP molecules is produced.• This energy is utilized by the living organisms to perform their various metabolic activities, and for maintaining their body temperature.• Water produced in the above reaction is retained in the body while decomposes to give carbon di oxide and hemoglobin.• Carbon di oxide is exhaled out and the haemglobin goes to the lungs for reuse.
• The above discussion makes it evident that the functions of hemoglobin in our body is to supply oxygen to various parts of the body.• Thus hemoglobin is an oxygen – carrier.
• In the oxygenation of a hemoglobin molecule, a proton, (H+ ) is also produced.• This proton reacts with bicarbonate dissolved in the blood to liberate carbon di oxide. HCO-3 + H+ ↔ H2 CO3 ↔ H2O + CO2 CO2 liberated as above is exhausted out.
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