Question

Which of the following statement(s) is (are) true about respiration?

(i) During inhalation, ribs move inward and diaphragm is raised .

(ii) In the alveoli, exchange of gases takes place i.e., oxygen from alveolar air diffuses into blood and carbon dioxide from the blood into the alveolar air .

(iii) Hemoglobin has a greater affinity for carbon dioxide than oxygen.

(iv) Alveoli increase surface area for exchange of gases.

• A. (i) and (iv)
• B. (ii) and (iii)
• C. (i) and (iii)
• D. (ii) and (iv)

Answer 1

The correct option is D

(ii) and (iv)

The correct option is D.

Explanation of correct option:

Statement (ii):

1. A biochemical process, which involves energy generation by combining glucose and oxygen, resulting in the release of water, carbon dioxide, and energy in the form of ATP (adenine triphosphate) is respiration.
2. The equation is: ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6+6{\mathrm{O}}_2\to 6{\mathrm{CO}}_2+6{\mathrm{H}}_2\mathrm{O}+\mathrm{energy}$
3. The respiratory system permits oxygen to enter the body and carbon dioxide to leave the body via the breathe-in and breathe-out process.
4. Millions of alveoli are present within the lungs, which function as the site of gaseous exchange.
5. An extensive network of blood vessels and blood capillaries are present here.
6. When one breathes in, oxygen is taken in by the alveoli and carbon dioxide is diffused out.

Statement (iv):

1. The presence of these many alveoli enhances the surface area of the lungs by many folds, and thus betters the exchange of gases.

Explanation of incorrect options:

Statement (i):

1. At the time of breathing, the air moves from the outside atmosphere into the lungs, the pressure in the lungs is required to be lower than atmospheric pressure.
2. During inhalation, the ribs move outwards and the diaphragm lowers or contracts to enhance the volume of the thoracic cavity.

Statement (iii):

1. Blood comprises a pigment known as hemoglobin, which possesses a greater affinity for oxygen in comparison to carbon dioxide.
2. The oxygen dissolved within the blood is taken in by the blood vessels surrounding the alveoli.

Final answer: The correct statements are (ii) and (iv).