Question

Which is the correct sequence of steps in respiration?
$a$. Transport of gases by the blood
$b$. Breathing or pulmonary ventilation
$c$. Cellular respiration
$d$. Diffusion of $O_2$ and $CO_2$ between blood and tissues
$e$. Diffusion of $O_2$ and $CO_2$ across alveolar membrane

• A. $b \to e \to a \to d \to c$
• B. $b \to a \to e \to c \to d$
• C. $b \to d \to a \to e \to c$
• D. $b \to e \to d \to a \to c$

Answer 1

Answer: (A)

Respiration involves the following steps :
(i) Breathing or pulmonary ventilation by which atmospheric air is drawn in and $CO_2$ rich alveolar air is released out.
(ii) Diffusion of gases $\left(O_2 and CO_2\right)$ across alveolar membrane.
(iii) Transport of gases by the blood.
(iv) Diffusion of $O_2$ and $CO_2$ between blood and tissues.
(v) Utilisation of $O_2$ by the cells for catabolic reactions and resultant release of $CO_2$ ( cellular respiration).