Test: Breathing & Exchange of Gases-2 - NEET MCQ

Exchange of gases at the lungs by simple diffusion.

Topic in NCERT: Exchange of gases

Line in NCERT: "exchange of o2 and co2 at the alveoli and tissues occur by diffusion."

A specialisedcentre present in the medulla region of the brain called respiratory rhythm centre is primarily responsible for this regulation. In the pons region of the brain called pneumotaxiccentre can moderate the functions of the respiratory rhythm centre.

Topic in NCERT: Regulation of respiration

Line in NCERT: "respiratory rhythm is maintained by the respiratory centre in the medulla region of brain. a pneumotaxic centre in the pons region of the brain and a chemosensitive area in the medulla can alter respiratory mechanism."

In insects, the respiration takes place through tracheal tubes which directly exchange gases with haemocoel and then with tissues.

Topic in NCERT: Insect respiration

Line in NCERT: "insects have a network of tubes (tracheal tubes) to transport atmospheric air within the body."

Nearly 20-25 per cent of CO₂ is transported by RBCs whereas 70 per cent of it is carried as bicarbonate. About 7 per cent of CO₂ is carried in a dissolved state through plasma acc. to ncert textbook.

Topic in NCERT: Transport of carbon dioxide

Line in NCERT: "nearly 20-25 per cent of co2 is transported by rbcs whereas 70 per cent of it is carried as bicarbonate."

RBCs contain a very high concentration of the enzyme carbonic anhydrase. This enzyme facilitates the reaction between CO2 and haemoglobin in both directions, aiding in the formation of carbamino-haemoglobin and its subsequent dissociation.

Topic in NCERT: Transport of gases

Line in NCERT: "rbcs contain a very high concentration of the enzyme, carbonic anhydrase and minute quantities of the same is present in the plasma too."

In the alveoli, there is high pO₂ , low pCO₂ , lesser H+ concentration and lower temperature,

The habit of Cigarette smoking can lead to coughing, emphysema and loss of cilia lining the respiratory tract. It contain nicotine that breaks the wall of alveoli to reduce respiratory surface.

Topic in NCERT: Disorders of respiratory system

Line in NCERT: "emphysema is a chronic disorder in which alveolar walls are damaged due to which respiratory surface is decreased. one of the major causes of this is cigarette smoking."

The increase in carbon dioxide (CO₂) levels triggers an increase in the lung ventilation rate as it signals a need for more oxygen to be obtained. This leads to an increased demand for oxygen, which increases respiratory rate and depth.

Topic in NCERT: Regulation of respiration

Line in NCERT: "increase in these substances can activate this centre, which in turn can signal the rhythm centre to make necessary adjustments in the respiratory process by which these substances can be eliminated."

RV = TLC - IRV – ERV– TV. On substituting the values, we get 1150ml.

Topic in NCERT: Respiratory volumes and capacities

Line in NCERT: "residual volume (rv): volume of air remaining in the lungs even after a forcible expiration. this averages 1100 ml to 1200 ml."

Respiration involves breathing or pulmonary ventilation by which atmospheric air is drawn in, Diffusion of gases across alveolar membrane, Transport of gases by the blood, Diffusion of gases between blood and tissues.Utilisation of oxygen by the cells.

Topic in NCERT: Respiration

Line in NCERT: "the first step in respiration is breathing by which atmospheric air is taken in (inspiration) and the alveolar air is released out (expiration). exchange of o2 and co2 between deoxygenated blood and alveoli, transport of these gases throughout the body by blood, exchange of o2 and co2 between the oxygenated blood and tissues and utilisation of o2 by the cells (cellular respiration) are the other steps involved."

• The alveoli are tiny air sacs in the lungs where the exchange of gases (oxygen and carbon dioxide) occurs. They are surrounded by a dense network of capillaries, allowing oxygen to diffuse into the bloodstream and carbon dioxide to diffuse out.
• The trachea and bronchi are part of the airways that transport air to and from the lungs but are not involved in gas exchange.
• The larynx is responsible for voice production and acts as a passageway for air but does not participate in gas exchange.

Topic in NCERT: Breathing and exchange of gases

Line in NCERT: "the alveoli and their ducts form the respiratory or exchange part of the respiratory system."

The correct statement regarding respiratory volumes is Option C. Tidal Volume (TV) is indeed the volume of air inspired or expired during a normal respiration, which typically averages about 500 mL. This volume represents the air moved during each breath cycle under resting conditions, not involving forced breathing. Options A, B, and D incorrectly describe the other respiratory volumes, misrepresenting their definitions and typical respiratory mechanics.

Topic in NCERT: Respiratory volumes and capacities

Line in NCERT: "tidal volume (tv): volume of air inspired or expired during a normal respiration. it is approx. 500 ml."

Option A is correct as both the Assertion and the Reason are true, and the Reason is indeed the correct explanation for the Assertion. Deoxygenated blood has a higher pCO2 because it reflects the CO2 levels after the blood has collected carbon dioxide from the tissues, where it is released as a waste product of metabolism. The elevated pCO2 then drives the diffusion of CO2 from the blood into the alveoli in the lungs, facilitating its exhalation. This process is crucial for maintaining the balance of gases and pH in the body.

Topic in NCERT: Transport of gases

Line in NCERT: "at the tissue site where partial pressure of co2 is high due to catabolism, co2 diffuses into blood (rbcs and plasma) and forms hco3 and h+."

The incorrect statement regarding the transport of gases in the blood is Option c. The enzyme carbonic anhydrase is not absent in RBCs; rather, it is highly abundant and plays a critical role in facilitating the rapid conversion of carbon dioxide and water into bicarbonate and hydrogen ions. This reaction is vital for the efficient transport of carbon dioxide from tissues back to the lungs. The presence of carbonic anhydrase in RBCs greatly enhances the blood’s capacity to carry carbon dioxide, which is primarily transported as bicarbonate.

Topic in NCERT: Transport of gases

Line in NCERT: "rbcs contain a very high concentration of the enzyme, carbonic anhydrase and minute quantities of the same is present in the plasma too."

Option D is correct because the Assertion is false and the Reason is true. Inspiratory Capacity (IC) is indeed the total volume of air a person can inspire after a normal expiration, but it is calculated by adding Tidal Volume (TV) and the Inspiratory Reserve Volume (IRV), not the Expiratory Reserve Volume (ERV). This error in the Assertion highlights a misunderstanding of the components that make up Inspiratory Capacity, which are TV and IRV, not TV and ERV.

Topic in NCERT: Respiratory volumes and capacities

Line in NCERT: "inspiratory capacity (ic): total volume of air a person can inspire after a normal expiration. this includes tidal volume and inspiratory reserve volume (tv+irv)."