Breathing and Exchange of Gases — Class 11 MCQs with Answers
Class 11 CBSE Biology · Chapter 14
90 practice questions · 30 Easy · 30 Medium · 30 Hard · Updated
Practise the most important Class 11 CBSE Biology questions from Chapter 14, "Breathing and Exchange of Gases". You get 9 timed quizzes made from 90 NCERT-based MCQs, with answers and explanations. The questions are split into 30 Easy, 30 Medium and 30 Hard. Warm up on the basics, then move on to the exam-level questions that set top scorers in CBSE & Maharashtra HSC Board exams, MHT-CET and NEET UG apart.
To score well in "Breathing and Exchange of Gases", focus on diagrams, key terms and knowing NCERT line by line. Each MCQ here is timed and uses exam-style marking (+4 correct, −1 wrong, 0 skipped). This trains you to stay accurate under time pressure, as real papers need. Every question has a short explanation, so a wrong answer becomes a quick lesson. It is the fastest way to fix gaps before a test.
Use this chapter for focused revision. Start with the Easy set to check your basics on Breathing and Exchange of Gases, then move to Medium and Hard to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 11 Biology mastery score. 14 sample questions are solved in full below, with the answer and a worked explanation. Sign in free to start practising.
Key concepts: Breathing and Exchange of Gases (Class 11 Biology)
Human respiration ends at the alveoli, where oxygen and carbon dioxide diffuse across a thin membrane along partial-pressure gradients. This chapter traces the conducting passages, the pressure-driven mechanics of breathing, respiratory volumes, and how blood ferries both gases between lungs and tissues.
- Respiratory organs
- Air travels through the nostrils, nasal chamber, pharynx, larynx, trachea, two primary bronchi and branching bronchioles ending in the alveoli of the lungs.
- Conducting vs exchange zone
- The passage from nostrils to terminal bronchioles conducts, warms and filters air; the alveoli form the respiratory part where actual gas exchange occurs.
- Inspiration
- Contraction of the diaphragm and external intercostals raises thoracic volume, dropping intra-pulmonary pressure below atmospheric so air rushes into the lungs.
- Expiration
- Relaxation of the diaphragm and intercostals shrinks the thorax, raising intra-pulmonary pressure above atmospheric; normal expiration is passive.
Breathing and Exchange of Gases — important questions & MCQs with answers (Class 11 Biology)
14 solved questions from this chapter's difficulty levels, each with its answer and explanation. The other 76 are timed and scored when you sign in.
- Q1Easy
Site of gas exchange in lungs:
A.Alveoli✓ CorrectB.BronchiC.TracheaD.LarynxAnswer: A. Alveoli
Explanation: Alveoli are the thin-walled, capillary-wrapped sacs where actual gas exchange happens; bronchi and trachea only conduct air without exchanging gases with blood.
- Q2Easy
Breathing or pulmonary ventilation refers to:
A.Gas exchange in tissuesB.Inhalation and exhalation of air between atmosphere and lungs✓ CorrectC.Glucose oxidationD.Production of ATPAnswer: B. Inhalation and exhalation of air between atmosphere and lungs
Explanation: Breathing (pulmonary ventilation) is just moving air between atmosphere and lungs; using O₂ to make ATP is cellular respiration, a separate process happening inside cells.
- Q3Easy
Hemoglobin (Hb) carries O₂ as:
A.CarboxyhemoglobinB.CarbaminohemoglobinC.Oxyhemoglobin (HbO₂)✓ CorrectD.MethemoglobinAnswer: C. Oxyhemoglobin (HbO₂)
Explanation: Haemoglobin carries O₂ as oxyhaemoglobin, formed when O₂ binds reversibly to the haem iron; carboxyhaemoglobin forms with CO instead, and carbaminohaemoglobin carries CO₂, not O₂.
- Q4Easy
Major muscle of breathing:
A.BicepB.Diaphragm✓ CorrectC.QuadricepsD.Cardiac muscleAnswer: B. Diaphragm
Explanation: The dome-shaped diaphragm contracts and flattens to enlarge thoracic volume during inspiration; intercostal muscles assist but the diaphragm does most of the work.
- Q5Easy
Earthworms breathe through their:
A.Moist cuticle (skin)✓ CorrectB.GillsC.TracheaD.LungsAnswer: A. Moist cuticle (skin)
Explanation: Earthworms lack lungs or gills entirely — gases diffuse directly across their thin, moist cuticle, so the skin must stay wet for respiration to work at all.
- Q6Easy
About what percent of O₂ in blood is transported by hemoglobin?
A.23%B.97%✓ CorrectC.50%D.3%Answer: B. 97%
Explanation: Haemoglobin carries about 97% of blood oxygen as oxyhaemoglobin; only the leftover 3% dissolves directly in plasma, which alone couldn't meet the body's O₂ demand.
- Q7Medium
Tidal volume (TV) of a healthy adult human is approximately:
A.500 mL✓ CorrectB.1500 mLC.3000 mLD.6000 mLAnswer: A. 500 mL
Explanation: Resting tidal volume is about 500 mL per breath at 12-16 breaths per minute — far smaller than vital capacity (~3500-4500 mL), the maximum forced exhale after deepest inhale.
- Q8Medium
Properties of an efficient respiratory surface include all EXCEPT:
A.Thick keratinised covering✓ CorrectB.Thin and moistC.Large surface areaD.Rich blood supplyAnswer: A. Thick keratinised covering
Explanation: An efficient respiratory surface must be thin and moist with a large area and rich blood supply; a thick keratinised covering, as on dry skin, blocks gas diffusion instead of aiding it.
- Q9Medium
Most O₂ in blood is carried by:
A.PlateletsB.Plasma dissolvedC.WBCD.Haemoglobin✓ CorrectAnswer: D. Haemoglobin
Explanation: About 97% of blood O₂ travels bound to haemoglobin as oxyhaemoglobin inside RBCs; only the remaining ~3% dissolves directly in plasma.
- Q10Medium
Vital capacity equals:
A.TV + ERV + RVB.TV + IRVC.ERV + TV + IRV✓ CorrectD.IRV + RVAnswer: C. ERV + TV + IRV
Explanation: Vital capacity is the maximum exhale after maximum inhale, equal to inspiratory reserve volume plus tidal volume plus expiratory reserve volume — it excludes residual volume, the air that never leaves the lungs.
- Q11Medium
Counter-current flow of water and blood in fish gills is advantageous because it:
A.Reduces blood volumeB.Saves energyC.Slows water flowD.Maintains O₂ gradient along entire lamella✓ CorrectAnswer: D. Maintains O₂ gradient along entire lamella
Explanation: Counter-current flow moves water and blood in opposite directions across the gill lamella, so water always meets less-oxygenated blood — maintaining an O₂ gradient along the whole lamella, not just saving energy.
- Q12Hard
Tidal volume is:
A.Maximum forced inhalationB.Air inhaled or exhaled in normal breath (~500 mL)✓ CorrectC.Residual volumeD.Vital capacityAnswer: B. Air inhaled or exhaled in normal breath (~500 mL)
Explanation: Tidal volume is the ~500 mL of air moved in a single normal breath at rest, not the maximal inhalation (inspiratory reserve) or the full exhale after deepest breath (vital capacity).
- Q13Hard
Assertion: Insects do not need a circulatory pigment for O₂ transport. Reason: Their tracheal system delivers O₂ directly to tissues.
A.Both true and Reason explains Assertion✓ CorrectB.Both true but Reason does not explainC.Assertion falseD.Both falseAnswer: A. Both true and Reason explains Assertion
Explanation: Both statements are true and the reason explains the assertion: insects' tracheal system delivers O₂ directly to tissues via tracheoles, so their haemolymph doesn't need a respiratory pigment like Hb.
- Q14Hard
Bohr effect: O₂ binding to Hb decreases when:
A.O₂ risesB.pH risesC.Temperature fallsD.CO₂/H⁺ increases (lower pH)✓ CorrectAnswer: D. CO₂/H⁺ increases (lower pH)
Explanation: The Bohr effect: rising CO₂ and H⁺ (falling pH) in tissues lowers Hb's O₂ affinity, so it unloads oxygen where it's needed most — the opposite of what happens in O₂-rich lungs.
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Start this chapter free →Breathing and Exchange of Gases — FAQs
What are the key concepts in Class 11 Biology Breathing and Exchange of Gases?+
Human respiration ends at the alveoli, where oxygen and carbon dioxide diffuse across a thin membrane along partial-pressure gradients. This chapter traces the conducting passages, the pressure-driven mechanics of breathing, respiratory volumes, and how blood ferries both gases between lungs and tissues. Key ideas include Respiratory organs, Conducting vs exchange zone, Inspiration, Expiration.
What does Class 11 Biology Chapter 14 (Breathing and Exchange of Gases) cover on XamBaaz?+
It has 90 NCERT-based MCQs on "Breathing and Exchange of Gases": 30 Easy, 30 Medium and 30 Hard. Together they make 9 timed quizzes, and you never get the same set twice. Every question has an instant explanation. They help you prepare for CBSE & Maharashtra HSC Board exams, MHT-CET and NEET UG.
Are these "Breathing and Exchange of Gases" questions free to practise?+
Yes. Sign in with Google to practise "Breathing and Exchange of Gases" free. Full unlimited access is ₹999/year on a launch offer until 1 December 2026. No chapter is charged separately.
How should I revise "Breathing and Exchange of Gases" for the exam?+
Start with the Easy quiz to check your basics, then try Medium and Hard to practise applying them. There are 9 timed quizzes on this chapter, so you can come back for a fresh set instead of one you have seen. Read each explanation, retry the questions you miss, and track your accuracy until it stays high.
Are these "Breathing and Exchange of Gases" MCQs available with answers?+
Yes. 14 sample questions are shown here in full, each with the correct option and a step-by-step "Why" explanation. Sign in free with Google to start practising, with instant scoring.
Is there negative marking in the "Breathing and Exchange of Gases" quizzes?+
Yes. The timed quizzes use exam-style marking: +4 for a right answer, −1 for a wrong one and 0 for a skip, the same negative marking as NEET UG. MHT-CET and CBSE board papers have no negative marking. Our mocks for those are scored their way.
What are the important questions from Breathing and Exchange of Gases (Class 11 Biology)?+
The questions that matter most test Respiratory organs, Conducting vs exchange zone, Inspiration, Expiration. This page shows 14 solved important MCQs with answers and explanations; all 90 questions on the chapter are available as timed quizzes once you sign in.
Is there an online quiz for Breathing and Exchange of Gases?+
Yes — Class 11 Biology Breathing and Exchange of Gases has timed online quizzes at Easy, Medium and Hard levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.