Haemoglobin is red because of the heme groups in its structure. Each hemoglobin protein is made up of subunits called hemes, which contain a red-colored compound called heme. This heme is crucial for carrying oxygen through the body. The iron molecules within the heme bind to oxygen, giving blood its characteristic red color.
The interaction between the iron and oxygen is what makes the blood appear red. Millions of red blood cells, each containing haemoglobin, contribute to the overall red color of blood.
