Question

Respiration involves following steps:
A. Diffusion of gases $O_2$ and ${CO}_2$ across alveolar membrane.
B. Transport of gases by blood.
C. Utilization of $O_2$ by cell for catabolic reaction and resultant release of $O_2$.
D. Pulmonary ventilation by which atmospheric air is drawn in and ${CO}_2$ rich air is released out.
E. Diffusion of $O_2$ and ${CO}_2$ between blood and tissue.

• A. $A\to B\to C\to D\to E$
• B. $E\to D\to C\to B\to A$
• C. $D\to A\to B\to E\to C$
• D. $C\to B\to E\to A\to D$

Answer 1

Answer: (C)

$D\to A\to B\to E\to C$

• Respiration involves the following steps:

(i) Breathing or pulmonary ventilation by which atmospheric air is drawn in and CO2 rich alveolar air is released out.

(ii) Diffusion of gases (O2 and CO2) across the alveolar membrane.

(iii) Transport of gases by the blood.

(iv) Diffusion of O2 and CO2 between blood and tissues.

(v) The utilisation of O2 by the cells for catabolic reactions and resultant release of CO2.

• Hence, Respiration involves the following steps above.
• So, the correct answer is 'D→A→B→E→C'.