Q.For completion of respiration process, write the given steps in sequential manner
a. Diffusion of gases (O2 and CO2) across alveolar membrane.
b. Transport of gases by blood.
c. Utilisation of O2 by the cells for catabolic reactions and resultant release of CO2.
d. Pulmonary ventilation by which atmospheric air is drawn in and CO2 rich alveolar air is released out.
e. Diffusion of O2 and CO2 between blood and tissues.

Putting the steps in their correct sequence: first comes pulmonary ventilation, by which atmospheric air is drawn in and carbon-dioxide-rich alveolar air is released out (d); next is the diffusion of oxygen and carbon dioxide across the alveolar membrane (a); this is followed by the transport of these gases by the blood (b); then comes the diffusion of oxygen and carbon dioxide between the blood and the tissues (e); and finally, the utilisation of oxygen by the cells for catabolic reactions, …

Respiration as a whole involves five stages, and understanding their order shows how oxygen makes its way from the atmosphere into the cells, and how carbon dioxide makes the reverse journey back out.

1. Breathing (pulmonary ventilation) — atmospheric air is drawn in and carbon-dioxide-rich alveolar air is pushed out. This is item (d) and comes first.
2. Diffusion at the alveoli — oxygen and carbon dioxide diffuse across the alveolar membrane between air and blood. This is item (a).
3. Transport by blood — these gases are carried throughout the body by the blood. This is item (b). …

Method: Sequencing the stages of a multi-step physiological process

This method applies to any question giving a jumbled list of stages from a process and asking you to put them in their correct order.

Steps

Step 1: Identify what the process as a whole accomplishes, start to finish

Before ordering the individual items, be clear on the overall journey the process describes — here, getting oxygen from the outside air into a cell, and getting carbon dioxide from a cell back out to the atmosphere.

Step 2: Ask, for each stage, what has to already be true before it can happen

For every listed stage, ask what earlier stage must have already occurred to make this one possible — for instance, gases cannot be exchanged at the alveoli until fresh air has actually reached the alveoli, and gases cannot be used by cells until they have already been delivered there by the blood.

Step 3: Chain the stages together using this dependency logic …