Question

Haemoglobin contains 0.33% of Fe by weight. If one molecule of haemoglobin contains two Fe atoms, the molecular weight of haemoglobin will be nearly:
(Atomic weight of Fe = 56)
A. 67000
B. 34000
C. 17000
D. 20000

Answer 1

Hint: For this problem, we have to use the formula of the mass percent of iron that is equal to the product of the atomic mass of iron and the number of atoms divided by the molecular mass of haemoglobin multiplied by 100.

Complete Step-By-Step Answer:
- In the given question we have to calculate the molecular weight of haemoglobin by using the given information.
- As we know that haemoglobin is the main constituent of blood which is made up of four subunits, two alpha units and two beta units, and also known as quaternary structure.
- The colour of the blood is red due to the presence of haemoglobin which is made up of two parts, globin and hemochromogen.
- It is given that the percentage weight of the iron is 0.33%. Also, one molecule of haemoglobin consists of 2 atoms of iron.
- So, we know that the atomic weight of one iron atom is 56 so the atomic weight of two iron atoms will be:
$\text{56 }\times \text{ 2 = 112g}$
- Mass percent is the method of determining the concentration of an element in the mixture of two or more elements.
- Now, by applying the formula of the mass percent of iron we can calculate the molecular weight of one molecule haemoglobin that is:
%Fe = ${\displaystyle \frac{\text{Weight of iron}}{\text{Molecular weight of compound}}}\times \text{ 100}$
$0.33={\displaystyle \frac{112}{\text{Molecular weight of compound}}}\times \text{ 100}$
- Molecular weight of haemoglobin = 33999.39 or 34000.

Therefore, option B is the correct answer.

Note: In the structure of haemoglobin, there are mainly three types of bonds that are hydrophobic interaction, hydrogen bonding and ion pairs which are present between the amino acids.