Problem 29 - Chemistry in 30 days

Question

Haemoglobin contains \(0.33 \%\) of iron by weight. The molecular weight of haemoglobin is approximately \(67200 .\) The number of iron atoms (at. wt. of \(\mathrm{Fe}=56\) ) present in one molecule of haemoglobin is (9) 6 (b) 1 (c) 4 (d) 2

Step-by-Step Solution

Answer

There are 4 iron atoms in one molecule of haemoglobin.

Step 1: Calculate the weight of iron in one molecule

Since haemoglobin contains 0.33% iron by weight, the weight of iron in one molecule of haemoglobin can be calculated using the formula: \[ \text{Weight of iron} = \frac{0.33}{100} \times 67200 = 222.72 \text{ amu} \]

Step 2: Determine the number of iron atoms

Each iron atom has an atomic weight of 56. To find the number of iron atoms, divide the total iron weight by the atomic weight of one iron atom: \[ \text{Number of iron atoms} = \frac{222.72}{56} \approx 4 \]

Step 3: Conclusion

The calculated number indicates that there are approximately 4 iron atoms in one molecule of haemoglobin, matching option (c).

Key Concepts

Haemoglobin

Haemoglobin is a complex protein found in red blood cells. It plays a crucial role in the transport of oxygen from the lungs to the rest of the body and carries carbon dioxide back to the lungs for exhalation.
Its structure is intricate and fascinating, composed of four subunits, each containing a heme group.
Each heme group has an iron atom, which is key in oxygen binding and transport.
Here's why haemoglobin matters:

• It increases the blood's ability to carry oxygen, thereby enhancing our capability to sustain life processes.
• It helps stabilize blood pH by managing carbon dioxide levels in the body.
• Its iron content is essential as it directly binds to oxygen.

Understanding its molecular weight, which is given in the exercise as approximately 67200 amu, allows scientists and medical professionals to perform calculations involving haemoglobin more effectively.

Atomic Weight

The concept of atomic weight is crucial in chemistry for numerous calculations. It represents the average mass of atoms of an element, measured in atomic mass units (amu).
For iron, its atomic weight is 56 amu.
This value is derived from isotopic masses and their relative abundance on Earth.
Atomic weight simplifies the process of determining the number of atoms in a molecule.

• Knowing that iron has an atomic weight of 56 amu helps in computing how many iron atoms constitute a given weight of iron in a compound.
• It's pivotal for converting mass data into mole and atom information, which is crucial for understanding reactions and compounds in chemistry.

Thus, using atomic weight, as we did in the exercise, allows calculation of the exact number of iron atoms present in haemoglobin.

Iron Atoms

Iron is an element known for its metallic properties and essential biological roles.
Each iron atom possesses unique characteristics:

• Its atomic number is 26, meaning it has 26 protons.
• It is a key component in haemoglobin, aiding in oxygen binding.
• Iron's ability to easily gain and lose electrons makes it vital in various reactions, including those in our bloodstream.

The exercise requires determining how many of these atoms are in haemoglobin using molecular and atomic weights.
We calculated that about 4 iron atoms are present in one haemoglobin molecule by dividing the weight of iron by the atomic weight of iron.
Calculations like these highlight the centrality of iron in maintaining our health and ensuring efficient oxygen transport.

Percentage Composition

Percentage composition refers to the percentage by weight of each element in a compound.
It's a fundamental concept, providing insight into the makeup of chemical substances.
In the exercise, we were given that iron constitutes 0.33% of haemoglobin’s weight.

• By understanding percentage composition, chemists can determine how much of each element is present.
• The exercise showed this by calculating the weight of iron in haemoglobin and using it to determine iron atom count.
• Such calculations are vital in developing pharmaceuticals and understanding nutrition.

Percentage composition not only aids in computations but also enhances understanding of molecular structure and functionality in biochemistry.