NEET ZoologyUpdated 19 Oct 2026

Breathing and Exchange of Gases: NEET PYQs and weightage

Breathing and Exchange of Gases carries 5.2 of 100 Zoology marks in NEET by past-paper share: 34 of the 648 tagged NEET Zoology PYQs in the ViJEEta bank (NEET 2013–2026). It ranks 9 of 17 Zoology chapters.

Take the 25-question Breathing and Exchange of Gases test Key facts ↓All NEET Zoology chapters

5.2/100 Weight in Zoology

Exam importance (4/5, by past-paper share)

34 NEET PYQs

463 Practice questions

396 With measured difficulty

How the weight is computed: this chapter's tagged NEET PYQs divided by all tagged NEET Zoology PYQs in the bank (34 of 648), times 100, with repeated questions counted once. The bank does not store the year of each NEET question, so none is printed. Computed from the bank at build time. Updated 19 Oct 2026.

Breathing and Exchange of Gases: key facts for NEET

16 facts the paper keeps asking, each with how it is asked. Copy it onto one page of your notebook: that page is this chapter's handbook.

Respiratory surfaces in animals
Sponges, coelenterates and flatworms exchange gases by simple diffusion over the whole body surface. Earthworms use their moist cuticle, and insects use tracheal tubes.
Asked as: "Site of gaseous exchange in an insect / earthworm?" or match animal $\leftrightarrow$ respiratory organ.
Trachea and bronchi
The trachea divides into right and left primary bronchi at the level of the 5th thoracic vertebra. Incomplete cartilaginous rings support the trachea, bronchi and initial bronchioles.
Asked as: "At which vertebra does the trachea bifurcate?" or "Which parts have incomplete cartilage rings?"
Conducting and exchange parts
The conducting part runs from the external nostrils to the terminal bronchioles. The exchange part is the alveoli and their ducts.
Asked as: "Diffusion occurs only in alveoli, why?" or "Terminal bronchiole belongs to which part?"
Mechanism of inspiration
Inspiration starts with the diaphragm contracting, which enlarges the thorax antero-posteriorly. The external intercostals lift the ribs and sternum, which enlarges it dorso-ventrally. Intra-pulmonary pressure then falls below atmospheric pressure.
Asked as: assertion-reason on which muscle changes which axis, or on negative pressure during inspiration.
Breathing rate and tidal volume
A healthy human breathes 12–16 times/min. Tidal volume (TV) is about $500 mL$ , so $6000$ – $8000 mL$ of air moves per minute. These volumes are measured with a spirometer.
Asked as: "Tidal volume of a healthy human in one hour?" ( $\approx 360$ – $480 L$ )
Reserve and residual volumes
Inspiratory reserve volume (IRV) is $2500$ – $3000 mL$ , expiratory reserve volume (ERV) is $1000$ – $1100 mL$ , and residual volume (RV) is $1100$ – $1200 mL$ .
Asked as: match volume $\leftrightarrow$ value, or calculate a capacity from the given volumes.
IC, EC and FRC
$IC = TV + IRV$
$EC = TV + ERV$
$FRC = ERV + RV$
Asked as: "Air left in lungs after a normal expiration?" $\to$ FRC
Vital capacity and total lung capacity
$VC = ERV + TV + IRV$
$TLC = VC + RV$
TLC is all four volumes.
Asked as: "Maximum air breathed out after a forced inspiration?" $\to$ VC, or "Which capacity includes RV?"
Partial pressures of O2 and CO2
$p O_{2}$ in mm Hg: atmosphere 159, alveoli 104, deoxygenated blood 40, oxygenated blood 95, tissues 40. $p C O_{2}$ : 0.3, 40, 45, 40, 45.
Asked as: " $p O_{2}$ and $p C O_{2}$ of atmospheric vs alveolar air?" $\to$ $p O_{2}$ higher, $p C O_{2}$ lower
Solubility and diffusion membrane
$C O_{2}$ is 20–25 times more soluble than $O_{2}$ . The diffusion membrane has 3 layers: alveolar squamous epithelium, basement substance, and capillary endothelium. Its total thickness is much less than $1 mm$ .
Asked as: "Why does $C O_{2}$ diffuse more per unit pressure difference?" or "Layers of the diffusion membrane?"
Transport of O2 and CO2
About $97%$ of $O_{2}$ travels in RBCs and $3%$ dissolved in plasma. For $C O_{2}$ , $20$ – $25%$ travels in RBCs as carbamino-haemoglobin, about $70%$ as bicarbonate and about $7%$ dissolved in plasma.
Asked as: "Major form of $C O_{2}$ transport?" $\to$ bicarbonate (not carbamino-Hb)
Haemoglobin and the dissociation curve
One haemoglobin molecule carries at most 4 $O_{2}$ . A plot of $%$ saturation vs $p O_{2}$ gives a sigmoid curve, the oxygen dissociation curve.
Asked as: "Shape of the $O_{2}$ dissociation curve?" or "Maximum $O_{2}$ molecules per Hb?"
Formation and dissociation of oxyhaemoglobin
Oxyhaemoglobin forms in the alveoli, where $p O_{2}$ is high, $p C O_{2}$ low, $H^{+}$ low and temperature lower. It dissociates in the tissues, where the opposite holds.
Asked as: "Which conditions favour $O_{2}$ unloading at tissues?" as a high/low combination question.
Carbonic anhydrase
Carbonic anhydrase is very concentrated in RBCs and present in minute amounts in plasma. It drives $C O_{2} + H_{2} O ⇌ H_{2} C O_{3} ⇌ HC O_{3}^{-} + H^{+}$ both ways: forward at the tissues, reverse at the alveoli.
Asked as: "Enzyme for bicarbonate formation, and where is it most concentrated?"
Gas delivered per 100 mL blood
Every $100 mL$ of oxygenated blood delivers about $5 mL$ of $O_{2}$ to tissues. Every $100 mL$ of deoxygenated blood delivers about $4 mL$ of $C O_{2}$ to the alveoli.
Asked as: a straight number recall, " $O_{2}$ delivered per $100 mL$ blood?"
Regulation of respiration
The respiratory rhythm centre is in the medulla. The pneumotaxic centre is in the pons and shortens inspiration. A chemosensitive area next to the rhythm centre responds to $C O_{2}$ and $H^{+}$ , and the role of $O_{2}$ in regulation is insignificant.
Asked as: "Pneumotaxic centre is located in?" $\to$ pons, or "Which gas mainly regulates breathing?" $\to$ $C O_{2}$

Trap

Students mix up residual volume and functional residual capacity. Air left after a *forced* expiration is residual volume (RV, 1100–1200 mL). Air left after a *normal* expiration is functional residual capacity (FRC = ERV + RV).

How does NEET ask Breathing and Exchange of Gases?

8 real previous-year questions from this chapter, as printed in the paper, each with its worked solution. Answer the first one here with no sign-in.

Q1ZoologyNEET UG PYQTransport of Gases

Try right here · No sign-in

Under normal physical conditions in human beings every 100 ml oxygenated blood can deliver____ml of O

_{2}

to the tissues.

Answer key (B) & worked solution

Correct answer: Option B

Every 100 ml of oxygenated blood can deliver around 5 ml of O

_{2}

to the tissues under normal physiological conditions.

Q2ZoologyNEET UG PYQRespiratory Volumes and Capacities

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?

A1700 mL

B2200 mL

C2700 mL

D1500 mL

Answer key (D) & worked solution

Correct answer: Option D

Tidal Volume = 500 ml Expiratory Reserve Volume = 1000 ml Expiratory Capacity = TV + ERV = 500 + 1000 = 1500 ml

Q3ZoologyNEET UG PYQSteps of Respiration

Mitochondrial inner membrane encloses

Acytosol

Bmucus

Caqueous humor

Dmatrix

Answer key (D) & worked solution

Correct answer: Option D

Mitochondrial inner membrane encloses matrix.

Q4ZoologyNEET UG PYQRespiratory Volumes and Capacities

Match the items given in Column I with those in Column II and select the correct option given below: Column IColumn IIaTidal Volume(i)2500-3000 mLbInspiratory Reserve volume(ii)1100-1200 mLcExpiratory Reserve volume(iii)500-550 mLdResidual Volume(iv)1000-1100 mL

Aa → (iii); b → (i); c → (iv); d → (ii)

Ba → (i); b → (iv); c → (ii); d → (iii)

Ca → (iii); b → (ii); c → (i); d → (iv)

Da → (iv); b → (iii); c → (ii); d → (i)

Answer key (A) & worked solution

Correct answer: Option A

Tidal volume is the volume of air inspired or expired during normal respiration. It is approximately 500 mL. Inspiratory reserve volume is an additional volume of air a person can inspire by a forceful inspiration. It is around 2500-3000 mL. Expiratory reserve volume is the additional volume of air a person can be exhaled by a forceful expiration. Its value is 1000 – 1100 mL. Residual volume is a volume of air remaining in the lungs even after forceful expiration. Its value is 1100 – 1200 mL.

Q5ZoologyNEET UG PYQRespiratory Organs in Animals

Sponges exchange O2 with CO2 by

Amoist cuticle

Btracheal tubes

Cgills

Dsimple diffusion over their entire body surfaces

Answer key (D) & worked solution

Correct answer: Option D

Lower invertebrates like sponges, coelenterates, flatworms, etc., exchange O2 with CO2 by simple diffusion over their entire body surfaces.

Q6ZoologyNEET UG PYQMechanism of Breathing

Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled that volume of air is due to

AResidual volume

BThere is a positive intrapleural pressure

CPressure in the lungs is higher than the atmospheric pressure

DThere is a negative pressure in the lungs

Answer key (A) & worked solution

Correct answer: Option A

Lungs do not collapse between breaths as some air always remains in the lung which can never be expelled because the negative intrapleural pressure is created by two opposing elastic forces pulling in the intrapleural space. The elastic lungs tend to collapse while the elastic chest wall tends to thrust outward. These two opposite forces create a negative intrapleural pressure which in turn opposes the natural tendency of lungs to collapse.

Q7ZoologyNEET UG PYQTransport of Gases

Identify the wrong statement with reference to transport of oxygen.

AHigher H

^{+}

conc. in alveoli favours the formation of oxyhaemoglobin

BLow pCO

_{2}

in alveoli favours the formation of oxyhaemoglobin

CBinding of oxygen with haemoglobin is mainly related to partial pressure of O

_{2}

DPartial pressure of CO

_{2}

can interfere with O

_{2}

binding with haemoglobin

Answer key (A) & worked solution

Correct answer: Option A

The Oxygen dissociation curve is highly useful in studying the effect of factors like pCO

_{2}

, H

^{+}

concentration, etc., on binding of O

_{2}

with haemoglobin. In the alveoli, where there is high pO

_{2}

, low pCO

_{2}

, lesser H

^{+}

concentration and lower temperature, favour the formation of oxyhaemoglobin. In the tissues, where low pO

_{2}

, high pCO

_{2}

, high H

^{+}

concentration and higher temperature exist, are favourable conditions for dissociation of oxygen from the oxyhaemoglobin.

Q8ZoologyNEET UG PYQDisorders of Respiratory System

Name the pulmonary disease in which alveolar surface area involved in gas exchange is drastically reduced due to damage in the alveolar walls.

APleurisy

BEmphysema

CPneumonia

DAsthma

Answer key (B) & worked solution

Correct answer: Option B

Emphysema is a pulmonary disease in which alveolar surface area involved in gas exchange is drastically reduced due to damage in the alveolar walls. It is often caused due to cigarette smoking.While asthma is a respiratory disorder in which there is difficulty in breathing due to inflammation of the bronchi and bronchioles.

Pleurisy- Inflammation of pleura that lines the lungs and chest cavity.

Pneumonia- Inflammation of one or both lungs due to infection.

Which topics in Breathing and Exchange of Gases carry the most questions?

All 11 topics, by tagged PYQs, then practice questions. Counted from the bank. Updated 19 Oct 2026.

Topic	PYQs	Practice questions
Disorders of Respiratory System	7	22
Respiratory Volumes and Capacities	6	58
Transport of Gases	5	99
Exchange of Gases	5	52
Respiratory Organs in Animals	4	28
Human Respiratory System	2	73
Mechanism of Breathing	2	54
Steps of Respiration	2	7
Breathing and Respiration - Introduction	1	7
Regulation of Respiration	0	48
Miscellaneous Examples	0	15

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Breathing and Exchange of Gases: NEET PYQs and weightage

Breathing and Exchange of Gases: key facts for NEET

Respiratory surfaces in animals

Trachea and bronchi

Conducting and exchange parts

Mechanism of inspiration

Breathing rate and tidal volume

Reserve and residual volumes

IC, EC and FRC

Vital capacity and total lung capacity

Partial pressures of O2 and CO2

Solubility and diffusion membrane

Transport of O2 and CO2

Haemoglobin and the dissociation curve

Formation and dissociation of oxyhaemoglobin

Carbonic anhydrase

Gas delivered per 100 mL blood

Regulation of respiration

How does NEET ask Breathing and Exchange of Gases?

Which topics in Breathing and Exchange of Gases carry the most questions?

Why does Breathing and Exchange of Gases show "–" until you answer 3 questions?

What happens when you test Breathing and Exchange of Gases?

Chapters either side of Breathing and Exchange of Gases by weight