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

The function of respiratory system does not deal with the cleaning up of the air.
Respiration involves the following steps:
(i) Breathing or pulmonary ventilation by which atmospheric air is drawn in and CO2 rich alveolar air is released out. (ii) Diffusion of gases (O2 and CO2 ) across alveolar membrane.
(iii) Transport of gases by the blood.
(iv) Diffusion of O2 and CO2 between blood and tissues.
(v) Utilisation of O2 by the cells for catabolic reactions and resultant release of CO2 (cellular respiration

Exchange of gases at the lungs by simple 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.

In central nervous system, regulation of respiratory rhythm during normal breathing is dependent upon concentration of carbon dioxide gas in air.

TV isapprox. 500 mL., i.e., a healthy man caninspire or expire approximately 6000 to 8000mL of air per minute. IRV averages 2500mL to 3000 mL.ERV averages 1000mL to 1100 mL. RV averages 1100 mL to 1200 mL.

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

Correct Answer :- a

Explanation : a) Carboxyhemoglobin (COHb) is formed when CO binds with hemoglobin with an affinity 200 times greater than oxygen, thereby decreasing oxygen-carrying capacity and the release of oxygen to tissues, leading to tissue hypoxia.

b)  The reason why the curves are different is because of the

different structures of myoglobin and haemoglobin. Myoglobin contains only a single globin chain: its dissociation curve is a rectangular hyperbola. Haemoglobin contains four globin chains and the oxygenation of each chain causes structural changes which increase the affinity of the haem of the remaining chains for oxygen. This consequence of subunit interaction is known as positive cooperativity and this increasing oxygen affinity as oxygen loads is the cause of the sigmoid shape of the dissociation curve.

Red blood cells and muscle cells carry out anaerobic respiration but RBC’s are permanently anaerobic and muscle cells are temporarily anaerobic in nature.

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.

When the carbon dioxide concentration in the blood increases, the respiratory rate will also increase to expel the excess carbon dioxide. This response is known as hyperventilation and is triggered by an increased level of CO₂ in the body.

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.

Atmospheric oxygen is less and hence more RBCs are needed to absorb the required amount of oxygen to survive.
At higher altitudes, the composition of air remains almost the same as at the sea level, but the density of the air gradually decreases. Number of red blood cells per unit volume is likely to be higher in a person living at high altitudes. This is in response to the air being less dense at high altitude. More number of red blood cells (more amount of hemoglobin) is needed to trap oxygen from the rarefied air having low pO₂.

Based on the given graph and the statements provided:

1. Statement i: During exercise, oxygen consumption rate in our body increases.

   • This is generally correct, as exercise increases the demand for oxygen.

2. Statement ii: Neural stimulus allows abdominal muscles, which are a kind of smooth muscle, to contract to facilitate ventilation while exercising.

   • This is partially correct, as neural stimulation does play a role in ventilation. However, abdominal muscles are actually skeletal muscles, not smooth muscles. So, this statement is inaccurate due to the muscle type mentioned.

3. Statement iii: Increase in ventilation during exercise prevents large changes in the partial pressure of O₂ or CO₂.

   • This is correct. Increased ventilation helps maintain stable levels of oxygen and carbon dioxide during exercise.

4. Statement iv: The overall impact is that the breathing rate increases.

   • This is also correct, as exercise typically increases the breathing rate.

Given this analysis, the correct answer is:

d) only i), iii), and iv) are correct.

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.

Statement i) is correct because chloride shift refers to the movement of chloride ions from red blood cells (RBCs) into the blood plasma. This helps to maintain the ionic balance between the RBCs and the blood plasma.

Statement ii) is correct because chloride shift is an important mechanism that helps to maintain ionic balance and chemical neutrality in the body. It ensures that the concentration of chloride ions remains balanced between the RBCs and the blood plasma.

Statement iii) is incorrect because chloride shift does not occur during the transport of CO₂. Instead, during CO₂ transport, bicarbonate ions are formed within the RBCs and then transported into the plasma in exchange for chloride ions. This process is known as the HCO₃- (bicarbonate) shift.

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.

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

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.

When pO₂ is low in the tissues, there is a higher binding of carbon dioxide to haemoglobin. This is because, in tissues, where pCO₂ is high and pO₂ is low, more binding of carbon dioxide to haemoglobin occurs.