Question

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Due to haemoglobin, the colour of the blood is red.
Reason R: Haemoglobin is a red coloured pigment.
In light of the above statements, choose the correct answer from the options given below

• A. Both A and R are true and R is the correct explanation of A
• B. Both A and R are true but R is NOT the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Hint:

The iron in haemoglobin acts as a chromophore when bound to oxygen.
This oxidation state change shifts light absorption, making oxyhaemoglobin bright red, while deoxyhaemoglobin appears darker red.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Blood pigmentation is determined by oxygen-carrying metalloproteins in blood cells.
In vertebrates, oxygen transport is mediated by haemoglobin.
Detailed Explanation:
Let us analyze Assertion A:
Blood contains red blood cells (erythrocytes) packed with haemoglobin.
This molecule binds to oxygen to form oxyhaemoglobin.
This complex gives blood its characteristic bright red color.
Thus, Assertion A is true.
Let us analyze Reason R:
Haemoglobin contains a heme group with an iron atom in the $Fe^{2+}$ state.
The coordination complex of iron with protoporphyrin absorbs light in the blue-green spectrum.
It reflects red wavelengths, making it a red-colored biological pigment.
Thus, Reason R is true.
Since the red color of blood is directly caused by the red pigment of haemoglobin, the reason directly explains the assertion.

Step 2: Final Answer:
Both Assertion A and Reason R are true, and Reason R is the correct explanation of Assertion A.