Question

Which of the following reactions prevails in red blood cells travelling through pulmonary capillaries?
A. $\text{Hb} + 4{O_2} → Hb(O_2)_4$
B. $\text{Hb}(O_2)_4 → Hb + 4{O_2}$
C. ${H_2}{CO_3} → H^{+} + HCO^{-3}$
D. $Hb + (CO_2)_4 → Hb(CO_2)_4$

Answer 1

Hint:
Blood is the medium for the transport of gases in the body. The blood acts as a medium for transport for both oxygen and carbon dioxide in the body. Blood carries oxygenated blood from the heart to the body tissues I.e. containing oxygen and deoxygenated blood from body tissues to the heart and thereby lungs.

Complete step by step answer:
In red blood cells, haemoglobin is a red coloured pigment which contains iron. The gases oxygen and carbon dioxide binds reversibly with haemoglobin at the alveolar level and tissue level.
Option -A- $\text{Hb} + 4{O_2} → Hb(O_2)_4$
This reaction occurs at the alveolar level. The haemoglobin in alveolar capillaries reversibly binds with oxygen following this reaction to form a compound named oxyhaemoglobin. This binding in alveoli occurs due to high partial pressure of oxygen, the low partial pressure of carbon dioxide, low temperature and hydrogen ion concentration. This is seen in alveolar capillaries.
Option -B- $\text{Hb}(O_2)_4 → Hb + 4{O_2}$
This reaction occurs at the tissue level. It is a dissociation reaction occurring at the tissue level to supply oxygen to tissues in the body. It is favourable when there is a low partial pressure of oxygen and higher partial pressure of carbon dioxide.
Option -C- ${H_2}{CO_3} → H^{+} + HCO^{-3}$
In Red blood cells, there is a very high concentration of an enzyme called carbonic anhydrase. This enzyme facilitates the binding of carbon dioxide at the tissue level following this reaction mentioned in the option thereby helps in eliminating carbon dioxide.
Option -D- $Hb + (CO_2)_4 → Hb(CO_2)_4$
Carbon dioxide at the tissue level is carried by the haemoglobin in the form of carbamino-haemoglobin in the percentage of 20-25 per cent. This helps in carrying carbon dioxide to the lungs. This binding is affected much by the partial pressure of both oxygen and carbon dioxide.
So, the correct answer to this question is the option"A". Because this reaction seems to occur at the alveolar level and known as oxygenation reaction.

Note:
Respiration is the process of exchange of gases between atmosphere and cells. It is carried out by different organs in different animals/species. In terrestrial animals including humans, lungs are the organs for the respiratory exchange of gases. Respiration is the most vital process for living.