NEET Previous Year Questions (2016-2024): Breathing & Exchange of Gases | Biology Class 11 PDF Download

2024

Q1: Which of the following factors are favourable for the formation of oxyhaemoglobin in alveoli?
(a) High pO₂ and High pCO_{2
(b) High} pO₂ and Lesser H⁺ concentration
_{(c) Low} pCO₂ and Lesser H⁺ concentration
(d) Low pCO₂ and High temperature
Ans: (b)
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.

Q2: Match List I with List II:

Choose the correct answer from the options given below :
(a) A-II, B-IV, C-I, D-III
(b) A-III, B-II, C-IV, D-I
(c) A-II, B-I, C-IV, D-III
(d) A-I, B-III, C-II, D-IV
Ans: (a)
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.

2023

Q1:  Vital capacity of lung is _________.      [2023]
(a) IRV + ERV
(b) IRV + ERV + TV + RV
(c) IRV + ERV + TV + RV
(d) IRV + ERV + TV
Ans: (d)

• 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.

2022

Q2: Which of the following statements are correct with respect to vital capacity?     (NEET 2022 Phase 2)
(a) It includes ERV, TV and IRV
(b) Total volume of air a person can inspire after a normal expiration.
(c) The maximum volume of air a person can breathe in after forced expiration.
(d) It includes ERV, RV and IRV.
(e) The maximum volume of air a person can breath out after a forced inspiration.
Choose the most appropriate answer from the options given below :
(a) (a) and (e)
(b) (b), (d) and (e)
(c) (a), (c) and (d)
(d) (a), (c) and (e)
Ans: (d)
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.

Q3: Under normal physiological conditions in human being every 100 ml of oxygenated blood can deliver ___________ ml of O₂ to the tissues.         (NEET 2022 Phase 1)
(a) 5 ml
(b) 4 ml
(c) 10 ml
(d) 2 ml
Ans: (a)

• 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.

Q4: Which of the following is not the function of conducting part of respiratory system        (NEET 2022 Phase 1)
(a) Inhaled air is humidified
(b) Temperature of inhaled air is brought to body temperature
(c) Provides surface for diffusion of O₂ and CO₂ 
(d) It clears inhaled air from foreign particles
Ans: (c)

• Option (d) is correct because the part starting with the external nostrils upto the terminal bronchioles constitute the conducting part; whereas the alveoli and their ducts form the respiratory or exchange part of the respiratory system.
• The conducting part transports the atmospheric air to the alveoli, clears it from foreign particles, humidifies and also bring the air to body temperature. Exchange part is the site of actual diffusion of O2/CO2 between blood and atmospheric air.

2021

Q1: The partial pressures (in mm Hg) of oxygen (O₂) and carbon dioxide (CO₂) at alveoli (the site of diffusion) are :     [NEET 2021]
(a) pO₂ = 95 and pCO₂ = 40
(b) pO₂ = 159 and pCO₂ = 0.3
(c)  pO₂ = 104 and pCO₂ = 40
(d) pO₂ = 40 and pCO₂ = 45
Ans: (c)

• Option (c) is correct because pO₂ in alveoli is 104 mm Hg and pCO₂ in alveoli is 40 mmHg. 
• In atmosphere, pO₂ is 159 mm Hg and pCO₂ is 0.3 mm Hg. 
• In deoxygenated blood, pO₂ is 40 mmHg and pCO₂ is 45 mmHg. 
• In oxygenated blood, pO₂ is 95 mmHg and pCO₂ is 40 mmHg. 

Q2: Select the favorable conditions required for the formation of oxyhemoglobin at the alveoli.      [NEET 2021]
(a) High pO₂, high pCO₂, less H⁺, higher temperature
(b) Low pO₂, low pCO₂, more H⁺, higher temperature
(c) High pO₂, low pCO₂, less H⁺, lower temperature
(d) Low pO₂ high pCO₂ more H⁺, higher temperature
Ans: (c)

• The factors favourable for the formation of oxyhaemoglobin at the alveolar level are; high pO₂, low pCO₂, less H⁺ concentration and lower temperature.
• The conditions favourable for the dissociation of oxygen from oxyhaemoglobin at the tissue level are; low pO₂, high pCO₂, high H⁺ concentration and high temperature. 

Q3: Assertion (A) : A person goes to high altitude and experiences 'altitude sickness' with symptoms like breathing difficulty and heart palpitations.
Reason (R) : Due to low atmospheric pressure at high altitude, the body does not get sufficient oxygen.
In the light of the above statements, choose the correct answer from the options given below:
(a) (A) is false but (R) is true
(b) Both (A) and (R) are true and (R) is the correct explanation of (A)
(c) Both (A) and (R) are true but (R) is not the correct explanation of (A)
(d) (A) is true but (R) is false              [NEET 2021]
Ans: (b)
Altitude sickness can be experienced at high altitude where body does not get enough oxygen due to low atmospheric pressure and causes nausea, fatigue and heart palpitations.
Hence, correct option is (b) as [R] is correct explanation of [A].

2020

Q1: Select the correct events that occur during inspiration.     [NEET 2020]
(i) Contraction of diaphragm
(ii) Contraction of external inter costal muscles
(iii) Pulmonary volume decreases
(iv) Intra pulmonary pressure increases
(a) (i), (ii) and (iv)
(b) Only (iv)
(c) (i) and (ii)
(d) (iii) and (iv)
Ans: (c)
Inspiration is initiated by the contraction of diaphragm, which increases the volume of thoracic chamber in the anterio-posterior axis. The contraction of external inter-coastal muscles lifts up the ribs and the sternum causing an increase in the volume of the thoracic chamber in the dorso-ventral axis.

Q2: Identify the wrong statement with reference to transport of oxygen.      [NEET 2020]
(a) Higher H⁺ conc. in alveoli favours the formation of oxyhaemoglobin 
(b) Low pCO₂ in alveoli favours the formation of oxyhaemoglobin 
(c) Binding of oxygen with haemoglobin is mainly related to partial pressure of O₂ 
(d) Partial pressure of CO₂ can interfere with O₂ binding with haemoglobin.
Ans: (a)
Higher H⁺ concentration favours the dissociation of oxygen from oxyhaemoglobin in tissues. In the alveoli, high pO₂, low pCO₂, lesser H⁺ concentration and lower temperature favour formation of oxyhaemoglobin. 

2019

Q1: Tidal Volume and Expiratory Reserve Volume of an athlete is 500 mL and 1000 mL respectively. What will be his expiratory capacity if the residual volume is 1200 mL?    [NEET 2019]
(a) 2700 mL
(b) 1500 mL
(c) 1700 mL
(d) 2200 mL
Ans: (b)
Expiratory Capacity (EC) is the total volume of air a person can expire after a normal inspiration. This includes tidal volume and expiratory reserve volume.
Since, Tidal Volume = 500 ml
And Expiratory Reserve Volume = 1000 ml
So, Expiratory Capacity = TV + ERV = 500 + 1000 = 1500 ml

2018

Q1: Which of the following options correctly represents the lung conditions in asthma and emphysema, respectively?    [NEET 2018]
(a) Inflammation of bronchioles; Decreased respiratory surface
(b) Increased number of bronchioles; Increased respiratory surface
(c) Increased respiratory surface; Inflammation of bronchioles
(d) Decreased respiratory surface; Inflammation of bronchioles
Ans: (a)

• Asthma is a difficulty in breathing, causing wheezing due to inflammation of bronchi and bronchioles. 
• Emphysema is a chronic disorder in which abnormal distension of the bronchioles or alveolar sacs of the lungs occurs due to which respiratory surface is decreased for the exchange of oxygen and carbon dioxide.

Q2: Match the items given in column I with those in column II and select the correct option given below.    [NEET 2018]

Ans: (b)

• Tidal volume(TV) is the volume of air inspired or expired during a normal respiration. It is approx. 500 mL.
• Inspiratory reserve volume(IRV) average 2500-3000 mL and is the additional volume of air inspired forcibly by a person.
• Expiratory reserve volume (ERV) is additional volume of air a person can be expired by a forceful expiration. This averages 1000 - 1100 mL.
• Residual volume (RV) is volume of air remaining in lungs even after forceful expiration. This averages 1100 - 1200 mL.

Q3: Which of the following is an occupational respiratory disorder?   [NEET 2018]
(a) Anthracis
(b) Silicosis
(c) Botulism
(d) Emphysema
Ans: (b)
Silicosis is an occupational disease caused due to excess inhalation of silica dust in the workers involved grinding or stone breaking industries.

2017

Q1: Lungs are made up of air-filled sacs, the alveoli. They do not collapse even after forceful expiration, because of    [NEET 2017]
(a) Inspiratory reserve volume
(b) Tidal volume
(c) Expiratory reserve volume
(d) Residual volume.
Ans: (d)
 Residual volume is the volume of air which remains in the lungs after the most forceful expiration. This residual air enables the lungs to continue exchange of gases even after maximum exhalation. Due to this, lungs do not collapse even after forceful expiration.

2016

Q1: The partial pressure of oxygen in the alveoli of the lungs is    [NEET 2016 Phase 2]
(a) Equal to that in the blood
(b) More than that in the blood
(c) Less than that in the blood
(d) Less than that of carbon dioxide.
Ans: (b)
The partial pressure of oxygen in alveolar air is 104mmHg whereas it is 40mmHg in deoxygenated blood and 95mmHg in oxygenated blood.

Q2: Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because    [NEET 2016 Phase 2]
(a) There is a negative pressure in the lungs
(b) There is a negative intrapleural pressure pulling at the lung walls
(c) There is a positive intrapleural pressure
(d) Pressure in the lungs is higher than the atmospheric pressure.
Ans: (b)
Intrapleural pressure is the pressure of air within the pleural cavity. Intrapleural pressure is always negative, which acts like a suction to keep the lungs inflated and prevent them from collapsing. The negative intrapleural pressure is due to three main factors: surface tension of the alveolar fluid; elasticity of lungs; elasticity of thoracic wall. Normally, there is a difference between intrapleural and intrapulmonary pressure, which is called transpulmonary pressure. This transpulmonary pressure creates the suction to keep the lungs inflated. If there is no pressure difference, there is no suction and lungs will collapse.

Q3: Reduction in pH of blood will       [NEET 2016 Phase 1]
(a) Decrease the affinity of haemoglobin with oxygen.
(b) Release bicarbonate ions by the liver
(c) Reduce the rate of heartbeat
(d) Reduce the blood supply to the brain.
Ans: (a)
Reduction of pH of blood will decrease the affinity of hemoglobin with oxygen which in turn causes acidosis.

Q4: Name the chronic respiratory disorder caused mainly by cigarette smoking.       [NEET 2016 Phase 2]
(a) Respiratory acidosis
(b) Respiratory alkalosis
(c) Emphysema
(d) Asthma
Ans: (c)
Emphysema results when the delicate linings of the air sacs in the lungs become damaged beyond repair. Most commonly, the toxins in cigarette smoke create the damage. Emphysema is called smoker’s disease.

Q5: Asthma may be attributed to      [NEET 2016 Phase 2]
(a) Inflammation of the trachea
(b) Accumulation of fluid in the lungs
(c) Bacterial infection of the lungs
(d) Allergic reaction of the mast cells in the lungs.
Ans: (d)
Asthma is an allergic condition in which the tissue surrounding the bronchioles of the lungs swell up and compress the bronchioles thus causing difficulty in breathing. This allergy mainly involves IgE antibodies and chemicals like histamine and serotonin from the mast cells.

2015

Q1: When you hold your breath, which of the following gas changes in blood would first lead to the urge to breathe?    [NEET 2015 / AIPMT 2015 ]
(a) Rising CO₂ concentration
(b) Falling CO₂ concentration
(c) Rising CO₂ and falling O₂ concentration
(d) Falling O₂ concentration
Ans: (a)
Excess CO₂ mainly stimulates the respiratory centre of the brain and increases the inspiratory and expiratory signals to the respiratory muscles. O₂ does not have a significant direct effect on the respiratory centre of the brain in controlling respiration. 

2014

Q1: Approximately seventy per cent of carbon dioxide absorbed by the blood will be transported to the lungs:    [NEET 2014 / AIPMT 2014 ]
(a) As bicarbonate ions
(b) In the form of dissolved gas molecules
(c) By binding to R.B.C.
(d) As carbamino - haemoglobin
Ans: (a) 

• About 70% of CO₂ (about 2.5ml per 100 ml. of blood), received by blood from the tissues, enters the RBCs where it reacts with water to form carbonic acid (H₂CO₃). 
• Carbonic anhydrase, exclusively found in RBCs, speeds up the formation of H₂CO₃ and rapidly converts it back to carbon dioxide and water when blood reaches the lungs. Almost as rapidly as formed, all carbonic acid of RBCs dissociates into hydrogen (H⁺) and bicarbonate ions (HCO^-₃$���3-$).