Question

Explain with reason: Human blood is red coloured.

Answer 1

Hint: The blood-coloring (haemochrome) matter is primarily caused by the oxygen transportation protein in the blood. Various organism groups use various proteins.

Complete Answer:
- Blood is a body fluid in animals and humans which provides the cells nutrients and oxygen and transports metabolic waste products far from those same cells. It is made up of blood cells found in plasma in vertebrates.
- The plasma, which accounts for 55% of the blood fluid, is mainly water containing proteins, mineral ions, glucose, hormones, carbon dioxide and the blood cells. Albumin is the plasma's primary protein which controls colloidal osmotic blood pressure. Blood cells are predominantly red blood cells also termed as RBCs and erythrocytes, white blood cells or leukocytes and platelets or thrombocytes.
- Red blood cells are the most common in the vertebrate blood. This includes hemoglobin, a protein containing iron that enables transport of oxygen by binding it reversibly to that respiratory gas and substantially enhancing its blood solubility. In comparison, carbon dioxide is often extracellularly transported in plasma as bicarbonate ions.
- Human blood is red because of the haemoglobin protein, which contains a red-colored compound called haeme, essential to the transportation of oxygen through the bloodstream. Haeme contains an iron atom, binding to oxygen. This molecule transfers oxygen from the lungs to other parts of the body.

Note: The main determinant of blood colour in vertebrates is hemoglobin. Each molecule has fourhaeme groups, and its colour changes due to its interaction with different molecules. Capillary blood and arterial blood are bright red in vertebrates and those that use haemoglobin because oxygen gives the haeme group a deep red colour. Deoxygenated blood is a richer shade of red; the shade can be seen by veins and blood samples are taken during donation. This is because of the variations between oxygenated and deoxygenated conditions in the light spectrum absorbed by hemoglobin.