Breathing and Exchange of Gases
14 solved NEET Biology previous year questions on Breathing and Exchange of Gases, each with the correct answer and a full explanation.
Q1
End products of aerobic respiration are
✓ Correct answer: c) carbon dioxide, water and energy
ExplanationCorrect Answer: C – Carbon dioxide, water and energy In aerobic respiration, one molecule of glucose is completely oxidized in the presence of oxygen to produce: Carbon dioxide (CO₂) – released as a waste product Water (H₂O) – formed during oxidative phosphorylation Energy (ATP) – used by the cell for various functions Hence, the end products of aerobic respiration are carbon dioxide, water, and energy.
Q2
Blood analysis of a patient reveals an unusually high quantity of carboxy- haemoglobin content. Which of the following conclusions is most likely to be correct? The patient has been inhaling polluted air containing unusually high content of:
✓ Correct answer: c) Carbon monoxide
ExplanationCarboxyhaemoglobin is a stable complex of carbon monoxide and haemoglobin that forms in RBCs upon contact with carbon monoxide.It has a greater affinity for haemoglobin than oxygen does.
Q3
Listed below are four respiratory capacities (i- iv) and four jumbled respiratory volumes of a normal human adult. Respiratory capacities Respiratory volumes (i) Residual volume (ii) Vital capacity (iii) Inspiratory reserve volume (iv) Inspiratory capacity Which one of the following is the correct matching of two capacities and volumes?
✓ Correct answer: c) (iv) , (i)
Explanation1. (i) Residual Volume (RV): The air remaining in lungs after forcible expiration.Standard Value: 1100 mL – 1200 mL.2. (ii) Vital Capacity (VC): The maximum volume of air a person can breathe in after a forced expiration (ERV + TV + IRV).Standard Value: 4000 mL – 4600 mL (Matches 4500 mL in the list).3. (iii) Inspiratory Reserve Volume (IRV): Additional volume of air a person can inspire by a forcible inspiration.Standard Value: 2500 mL – 3000 mL (Matches 2500 mL in the list).4. (iv) Inspiratory Capacity (IC): Total volume of air a person can inspire after a normal expiration (TV + IRV). | | NEET Standard Value: 3000 mL – 3500 mL (Matches 3500 mL in the list).
Q4
The partial pressure of oxygen in the alveoli of the lungs is:
✓ Correct answer: b) more than that in the blood
ExplanationThe partial pressure of oxygen (pO₂) in the alveoli of the lungs is higher than in the deoxygenated blood arriving via pulmonary arteries.In alveoli, pO₂ is around 104 mmHg, while in deoxygenated blood it is about 40 mmHg.This difference allows oxygen to diffuse from alveoli into the blood.Carbon dioxide moves in the opposite direction due to its higher partial pressure in blood.This gas exchange maintains proper oxygenation of blood for delivery to body tissues.
Q5
Reduction in of blood will
✓ Correct answer: b) Decrease the affinity of haemoglobin with oxygen
ExplanationA reduction in blood pH (increased acidity) decreases the affinity of hemoglobin for oxygen.This is explained by Bohr’s effect, where an increase in H⁺ ions (lower pH) causes hemoglobin to release more oxygen, facilitating oxygen delivery to tissues.This mechanism is particularly important during high metabolic activity when carbon dioxide production increases, lowering pH.Hence, the correct answer is option B.
Q6
Name the chronic respiratory disorder caused mainly by cigarette smoking:
✓ Correct answer: a) Emphysema
Explanation(1) 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. [New NCERT Class 11th Page No. 190]
Q7
Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because
✓ Correct answer: b) there is a negative intrapleural pressure pulling at the lung walls
ExplanationThe lungs do not collapse between breaths because of the negative intrapleural pressure (pressure in the space between the lungs and chest wall).This negative pressure creates a suction effect, keeping the lungs inflated by constantly pulling the lung walls outward.It balances the natural elastic recoil of the lungs that tends to make them collapse.Additionally, residual volume of air remains in the lungs even after forceful expiration, ensuring continuous gas exchange and preventing lung collapse.
Q8
Lungs are made up of air-filled sacs the alveoli. They do not collapse even after forceful expiration, because of:
✓ Correct answer: a) Residual Volume
ExplanationResidual volume (RV): Volume of air remaining in lungs even after a forcible expiration.It is about .Residual volume is involved in maintaining the patency of alveoli.
Q9
Tidal volume and expiratory reserve volume of an athlete is 500mL and 1000mL respectively. What will be his expiratory capacity if the residual volume is 1200mL?
✓ Correct answer: c) 1500 mL
ExplanationFormula: Given: TV = 500 mL ERV = 1000 mL Residual Volume (RV) = 1200 mL (not needed here). 📌 Calculation:
Q10
Select the correct events that occur during inspiration. (1) Contraction of diaphragm (2) Contraction of external inter-costal muscles (3) Pulmonary volume decreases (4) Intra pulmonary pressure increases [NEET 2020]
✓ Correct answer: a) (1) and (2)
ExplanationInspiration (inhalation) is the process of drawing air into the lungs, and it involves several mechanical changes: Correct Events: (1) Contraction of diaphragm The diaphragm contracts and moves downward, increasing the volume of thoracic chamber in the antero-posterior axis.(2) Contraction of external inter-costal muscles These muscles lift the rib cage up and outward, causing an increase in the volume of the thoracic chamber in the dorso-ventral axis.As a result of (1) and (2), thoracic volume increases, which leads to: Decrease in intrapulmonary pressure (not increase) Increase in pulmonary volume (not decrease) This pressure drop causes air to flow into the lungs Incorrect Events: (3) Pulmonary volume decreases – Incorrect, it increases during inspiration (4) Intra pulmonary pressure increases – Incorrect, it decreases to allow air inflow Final Answer: A. (1) and (2)
Q11
Select the favourable conditions required for the formation of oxyhaemoglobin at the alveoli.
✓ Correct answer: d) High , low , less , lower temperature
ExplanationIn the alveoli, the factors favourable for the formation of oxyhaemoglobin are high , low , lesser concentration and lower temperature.In the tissue, the factors favourable for the dissociation of oxyhaemoglobin are low , high , high concentration and high temperature.
Q12
Which of the following is not the function of conducting part of respiratory system ? [NEET 2022]
✓ Correct answer: c) Provides surface for diffusion of and
Explanation(3) Explanation: The conducting part of the respiratory system includes the nostrils, pharynx, larynx, trachea, bronchi, and bronchioles.Its primary functions are: ✔ Filtering inhaled air (removing dust/particles). ✔ Humidifying air to prevent dryness. ✔ Bringing air to body temperature for efficient gas exchange.Gas diffusion (exchange of O₂ and CO₂) does not occur in the conducting part; it takes place in the alveoli, which belong to the respiratory part.
Q13
Bulk of carbon dioxide ( ) released from body tissues into the blood is present as:
✓ Correct answer: c) Bicarbonate in blood plasma and RBCs
ExplanationThe bulk of carbon dioxide (CO₂) released from body tissues into the blood is transported mainly as bicarbonate ions (HCO₃⁻).About 70% of CO₂ enters red blood cells, where it is converted to carbonic acid by carbonic anhydrase and then dissociates into bicarbonate and hydrogen ions.The bicarbonate then diffuses into the blood plasma (with chloride shift maintaining ionic balance).A smaller fraction is transported as carbamino-haemoglobin (~20–25%) and an even smaller amount as dissolved CO₂ (~5– 10%).Therefore, the correct option is C: Bicarbonate in blood plasma and RBCs.
Q14
The Total Lung Capacity (TLC) is the total volume of air accommodated in the lungs at the end of a forced inspiration. This includes:
✓ Correct answer: c) RV (Residual volume); ERV (Expiratory Reserve Volume); TV (Tidal Volume); and IRV (Inspiratory Reserve Volume)
ExplanationTotal Lung Capacity: Total volume of air accommodated in the lungs at the end of a forced inspiration.This includes RV, ERV, TV and IRV or vital capacity + residual volume.Total Lung Capacity (TLC) is the sum of all lung volumes present after forced inspiration.TLC = RV + ERV + TV + IRV
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