Question

Red blood cells are red, due to the presence of
(a)Haemocyanin
(b)Haemoglobin
(c)Serotonin
(d)Epinephrine

Answer 1

Hint: RBCs contain a metalloprotein responsible for oxygen transfer. It is an iron-containing protein that has a quaternary structure with multi-subunit globular protein. This structure consists of a heterocyclic ring called a porphyrin ring.

Complete answer:
Red blood cells are red, due to the presence of Haemoglobin. The haemoglobin is made up of four subunits called heme, which binds to the iron. When the iron of heme binds with the oxygen coming from the alveoli of the lungs, it imparts the RBCs a red colour. It is the interaction between iron and oxygen due to which the red colour appears.

Additional Information: Haemoglobin comprises about 96% of the dry matter of the RBC. Haemoglobin develops in the bone marrow that becomes red blood cells. When red cells die, haemoglobin is broken down, iron is salvaged, transported to the bone marrow by proteins called transferrins, and used again in the production of new red blood cells. The remainder of the haemoglobin forms the basis of bilirubin, which is excreted into the bile and gives the faeces their characteristic yellow-brown colour.
Haemoglobin S is a form of haemoglobin that is present in a person who has sickle cell anaemia, a hereditary disorder, in which the cells become sickle-shaped when oxygen is lacking.
Haemocyanin: It is the protein which transports oxygen in the bodies of some invertebrates. Haemocyanin has two copper atoms in their active centres which reversibly binds to a single oxygen molecule. It is blue in colour when oxygenated and colourless when oxygen is removed.
Serotonin: It is a chemical that is mainly found in the brain, bowels, and blood platelets. The key role of serotonin is maintaining mood balance and it also contributes to wellbeing and happiness.
Epinephrine: It is also called adrenaline hormone which is secreted by the medulla of the adrenal gland. It primarily increases the cardiac output and also increases the glucose levels in the blood.
So, the correct answer is ‘Haemoglobin’.

Note: -Haemoglobin has a high affinity for oxygen but has a higher affinity for CO, carbon monoxide, so in a room with less oxygen and a considerable amount of CO, it will lead to a combination of CO and Haemoglobin, called carboxyhemoglobin, which leads to asphyxiation.
-Low haemoglobin leads to anaemia, which can be cured by eating iron-rich contents.
-Erythrocytes or RBCs are oval biconcave disk-shaped and lack a nucleus.