31 Years NEET Previous Year Questions: Breathing & Exchange of Gases Free

Emphysema (A-II):

• Emphysema is a chronic respiratory disease where there is damage to the alveolar walls. This results in larger but fewer alveoli, reducing the surface area for gas exchange, causing shortness of breath. One of the major causes of cigarette smoking.

Angina Pectoris (B-III):​

• A symptom of acute chest pain appears when no enough oxygen is reaching the heart muscle.
• Angina can occur in men and women of any age but it is more common among the middle-aged and elderly. It occurs due to conditions that affect the blood flow.

Glomerulonephritis (C-IV):

• Glomerulonephritis is the inflammation of the glomeruli in the kidneys, which are responsible for filtering blood.
• This condition can result from infections, immune disorders, or other systemic conditions. It often leads to proteinuria (protein in urine), hematuria (blood in urine), and reduced kidney function.

Tetany (D-I):

• Tetany is a condition characterized by rapid, involuntary muscle spasms.
• It is caused by low levels of calcium ions (Ca++) in body fluids, which affect muscle and nerve function.

• E - Breathing or pulmonary ventilation: This is the process of moving air in and out of the lungs, also known as inhalation and exhalation.
• A - Diffusion of gases across alveolar membrane: In the lungs, oxygen diffuses from the alveoli (air sacs) into the blood, and carbon dioxide diffuses from the blood into the alveoli to be exhaled.
• C - Transport of gases by blood: Once the gases are exchanged in the alveoli, the oxygen is carried by the blood (mostly by red blood cells) to tissues, while carbon dioxide is transported back to the lungs for removal.
• B - Diffusion of gases between blood and tissues: In the tissues, oxygen diffuses from the blood into the cells, and carbon dioxide diffuses from the cells into the blood.
• D - Utilization of O₂ by the cells for catabolic reactions: Inside the cells, oxygen is used for cellular respiration, a process that helps produce energy for the cell’s functions, and carbon dioxide is produced as a byproduct.

Thus, the correct order of steps is E → A → C → B → D.

First, let's define each term listed in List I and match them with their appropriate descriptions in List II.

List I:

• Expiratory Capacity (EC): This is the maximum volume of air that a person can expel from the lungs after a normal tidal expiration. It is composed of the expiratory reserve volume (ERV) and tidal volume (TV).
• Functional Residual Capacity (FRC): This represents the volume of air present in the lungs at the end of a passive expiration. It is the sum of the residual volume (RV) and the expiratory reserve volume (ERV).
• Vital Capacity (VC): This includes the total volume of air that can be expelled from the lungs after taking as deep an inhalation as possible. Hence, this comprises the tidal volume (TV), inspiratory reserve volume (IRV), and the expiratory reserve volume (ERV).
• Inspiratory Capacity (IC): It refers to the volume of air that can be inhaled after a normal expiration. This combines tidal volume (TV) and inspiratory reserve volume (IRV).

List II:

• I. Expiratory reserve volume + Tidal volume + Inspiratory reserve volume = Vital Capacity (VC).
• II. Tidal volume + Expiratory reserve volume = Expiratory Capacity (EC).
• III. Tidal volume + Inspiratory reserve volume = Inspiratory Capacity (IC).
• IV. Expiratory reserve volume + Residual volume = Functional Residual Capacity (FRC).

Now, let's match the terms:

A (Expiratory Capacity) matches with II.
B (Functional Residual Capacity) matches with IV.
C (Vital Capacity) matches with I.
D (Inspiratory Capacity) matches with III.

The correct option that pairs these correctly is: Option A: A-II, B-IV, C-I, D-III.

The formation of oxyhemoglobin in the alveoli is primarily influenced by the partial pressure of oxygen ( pO₂ ), partial pressure of carbon dioxide ( pCO₂), hydrogen ion concentration ( H⁺ ), and temperature. Understanding these factors will help in selecting the right option that describes the conditions favorable for maximizing the binding of oxygen to hemoglobin in the lungs.
1. Oxygen Partial Pressure ( pO₂ ): High pO 2 enhances the formation of oxyhemoglobin. In the alveoli, where gas exchange occurs, the pO₂ is relatively high, making it a favorable condition for oxyhemoglobin formation as oxygen molecules bind readily to hemoglobin.
2. Carbon Dioxide Partial Pressure ( pCO₂ ): Lower pCO₂ is favorable in the alveoli for oxyhemoglobin formation. High pCO₂ leads to a lower pH (due to formation of carbonic acid), which can cause the release of O₂ from hemoglobin (Bohr effect), reducing hemoglobin's affinity for oxygen.
3. Hydrogen Ion Concentration ( H⁺): Lesser H⁺ concentration, or higher pH, increases the affinity of hemoglobin for oxygen. In alkaline conditions (higher pH), hemoglobin is more likely to bind oxygen, thus forming oxyhemoglobin.
4. Temperature: Temperature also affects oxygen binding. Lower temperatures generally enhance the uptake of oxygen by hemoglobin. However, since the lung environment maintains a stable temperature, significant fluctuations in temperature are less of a consideration in this context compared to pO₂ , pCO₂ , and H⁺ concentration. Given these points, Option B - High pO₂ and Lesser H⁺ concentration - best describes the conditions that are favorable for the formation of oxyhemoglobin in the alveoli. High pO₂ ensures that more oxygen molecules are available to bind with hemoglobin, and a lower H⁺ concentration (higher pH) reduces the release of oxygen from hemoglobin, thereby increasing oxygen uptake.

• The vital capacity (VC) of the lung is the maximum amount of air a person can expel from the lungs after a maximum inhalation. It is equal to the sum of inspiratory reserve volume (IRV), tidal volume (TV), and expiratory reserve volume (ERV).
• Inspiratory reserve volume (IRV) is the amount of air that can be inhaled beyond a normal breath.
• Expiratory reserve volume (ERV) is the amount of air that can be exhaled beyond a normal breath.
• Tidal volume (TV) is the amount of air that is inhaled and exhaled during a normal breath.

Therefore, vital capacity (VC) = IRV + ERV + TV.

Option (d) is the correct answer because statements (a), (c) and (e) are correct.

• Vital capacity includes ERV, TV and IRV.
• Vital capacity is the maximum volume of air a person can breathe in after a forced expiration or the maximum volume of air a person can breathe out after a forced inspiration.
• Statement (b) is incorrect as total volume of air a person can inspire after a normal expiration is termed as inspiratory capacity (IC).
• Statement (d) is incorrect as ERV, RV, IRV and TV comprise total lung capacity.

• The respiratory system is divided into conducting zone and a respiratory zone.
• Conducting zone starts from the nose and ends in the bronchioles.
• The respiratory zone includes terminal bronchioles and alveoli.
• The conduction zone has different functions such as, it clears the inhaled air from foreign particles, humidifying the inhaled air, and also bringing the temperature of the inhaled air to body temperature.
• The respiratory zone is the site for an exchange of gases such as oxygen and carbon dioxide.

• Option (b) is the correct answer because every 100 ml of oxygenated blood can deliver around 5 ml of O₂ to the tissues under normal physiological conditions.
• Option (c), (d) and (a) are incorrect because every 100 ml of deoxygenated blood delivers approximately 4 ml of CO₂ to the alveoli.

In the alveoli, where there is high pO₂, low pCO₂, lesser H⁺ concentration and lower temperature, the factors are all favourable for the formation of oxyhaemoglobin, whereas in the tissues, where low pO₂, high pCO₂, high H⁺ concentration and higher temperature exist, the conditions are favourable for dissociation of oxygen from the oxyhaemoglobin.