FREE NEET Biology Practice MCQ Test: Breathing And Exchange Of Gases Exercise 4 Questions Answers With Detailed Explanations [PDF]

Answer: (b)

At high altitudes, arterial $pO_2$ decreases as density of air decreases. Number of RBCs per unit volume of blood is likely to be higher in a person living at high altitudes. More number of RBCs are needed to trap O₂ from air having less O₂ .

Answer: (b)

Answer: (d)

Answer: (d)

During oxygen transport, when $O_{2}$ tension is low and $CO_{2}$ tension is high in the tissues, the oxyhaemoglobin at the tissue level liberates oxygen to the cells.

Answer: (d)

Answer: (d)

Excess $CO_2$ mainly stimulates the respiratory centre of the brain and increases the inspiratory and expiratory signals to the respiratory muscles. $O_2$ does not have a significant direct effect on the respiratory centre of the brain in controlling respiration.

Answer: (d)

Actively respiring tissues require more oxygen. They are also associated with high partial pressures of carbon dioxide since it is a product of respiration. The curves show that oxygen would be more readily released at higher partial pressures of carbon dioxide, i.e. at active tissues.

Answer: (c)

Answer: (b)

Answer: (a)

A large proportion of oxygen is left unused in human blood even after its uptake by the body tissue, can acts as reserve during muscular exercise because our tissues are able to utilize only 25% of $O_{2}$ carried by arterial blood. Our venous blood is still 75% saturated with $O_{2}$

Answer: (c)

Answer: (a)

Answer: (d)

Answer: (a)

In the lung, each alveolar duct opens into a blind chamber, the alveolar sac, or infundibulum. The latter consists of a central passage giving off several small pouches, the alveoli, or air sacs on all sides. The air sacs give the infundibulum the appearance of a small bunch of grapes. The alveoli have a very thin (0.0001 mm thick) wall composed of simple moist, nonciliated, squamous epithelium. The number of alveoli is countless and their surface area enormous. This further accelerates the gaseous exchange in the alveoli.

Answer: (c)

Answer: (d)

Answer: (d)

Answer: (a)

Answer: (d)

Brain is the most vital organ. It stops functioning in the absence of $O_2$.

Answer: (d)

Diffusion is the net flow of a substance from a region of higher concentration to a region of lower concentration. The exchange of gases between the alveoli and blood in the lung is the result of difference in partial pressure of respiratory gases. The partial pressure of oxygen (p$O_2$) of the alveolar air is higher than the p$O_2$ of blood in alveolar capillaries, thus $O_2$ diffuses rapidly from the alveolar air into the blood of alveolar capillaries. The p$CO_2$ of blood reaching the alveolar capillaries is higher than the p$CO_2$ of alveolar air. Therefore, $CO_2$ diffuses into the alveolar air.