Question

Haemoglobin contains 0.33% of iron by weight. The molecular weight of haemoglobin is approximately 67200. Find out the number of iron atoms (at. wt. of Fe = 56) present in the molecule of haemoglobin. Explain how interaction of carbon monoxide with haemoglobin makes it poisonous ?

Answer 1

i) Given molecular weight of hemoglobin is 67200

It contains nearly 0.33% iron by weight

Atomic weight of Fe is 56

Assume in 100g hemoglobin, only 0.33% grams of Fe is present  

Therefore, 100 – 0.33 = 99.67

Moles of hemoglobin = 99.67/67200

= 0.00148

Moles of iron present in the hemoglobin = 0.33/56

                                                                              = 0.00589

Now consider z/67200 moles of Hemoglobin contains 0.00589 moles

Therefore the   number of moles of iron present in one molecule of hemoglobin is equal to = $0.00589 \times N \frac {z}{0.00148} \times Nz$ = 3.9 = 4

ii) The hemoglobin present in the RBC of our body binds with oxygen in the lungs and distributes oxygen throughout the body. Hemoglobin has a higher affinity towards oxygen.

The carbon monoxide occupies the three binding sites of oxygen in hemoglobin and inhibits the distribution of oxygen throughout the body which makes blood cells dead.