One third of the mass of human blood is made of the protein hemoglobin; it is re
ID: 68186 • Letter: O
Question
One third of the mass of human blood is made of the protein hemoglobin; it is responsible for the transport of oxygen to the cells. A reasonable estimate of the molecular weight of a protein can be made from the knowledge of the number of independent (non-covalently linked) chains and the sulfide bonding characteristics. There are 4 separate peptide chains in hemoglobin. Two of the chains are composed of 141 amino acids each and the other two of 146 amino acids each. Assume the average MW of an unbonded amino acid is 128. Hemoglobin has no disulfide bonds. (MW of hydrogen = 1, MW of oxygen = 16) Estimate the molecular weight of hemoglobin using the average molecular weight of an amino acid given above for each amino acid, and accounting for the number of chains and the change in MW due to peptide and disulfide bonds.Explanation / Answer
10. The total mol wt of hemoglobin with 4 peptide chains would be 73,472.
For the formation of the peptide bond, one molecule of water molecule is released. For the formation of all peptide bonds in the hemoglobin total of 570 molecules of water are released. (570 x 18= 10,260 )
Subtract the mol wt from the original mol wt to get the actual weight of the hemoglobin to be 63,212
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