Q. The red colour of human blood is due to ____:
Answer: Haemoglobin
Notes: Human blood is red because hemoglobin, which is carried in the blood and functions to transport oxygen, is iron-rich and red in color. In its oxygenated state it is called oxyhemoglobin and is bright red. In the reduced state it is called deoxyhemoglobin and is purple-blue. Each hemoglobin molecule is made up of four heme groups surrounding a globin group. Heme contains iron and gives a red color to the molecule.