Which component of tobacco smoke contains most of the carcinogens linked to lung cancer?
Correct answer C. Tar
Topic / 45 questions
Respiration and Gaseous Exchange MCQs
Respiration MCQs are multiple-choice questions on the human respiratory system, covering the air passages, the mechanism of breathing, gas exchange in the alveoli, transport of gases in the blood and the effects of smoking. Every question on MCQs360 shows the correct answer instantly, so you can check your answers while you revise.
- Biological Molecules 74
- Coordination and Control 72
- Biology Diagnostic 70
- Cell Structure and Function 67
- Biotechnology 65
- Reproduction 58
- Bioenergetics 55
- Circulation 50
- Inheritance 48
- Digestion 45
- Immunity 45
- Support and Movement 45
- Acellular Life (Viruses) 45
- Homeostasis 45
- Respiration and Gaseous Exchange 45
- Evolution 45
- Enzymes 45
- Cell Cycle 41
- Chromosome and DNA 40
- Biology Introduction 38
- Ecosystem 27
Compared with adult haemoglobin, where does the oxygen dissociation curve of fetal haemoglobin lie?
Correct answer A. To the left, because fetal haemoglobin has a higher affinity for oxygen
Myoglobin in muscle releases its oxygen only when partial pressure of oxygen becomes very low. What does this show?
Correct answer A. Myoglobin has a higher affinity for oxygen than haemoglobin
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Why is carbon monoxide from car exhaust and cigarette smoke dangerous?
Correct answer D. It forms stable carboxyhaemoglobin and reduces the oxygen-carrying capacity of blood
How does a rise in body temperature, as in exercising muscle, affect haemoglobin?
Correct answer C. Its affinity for oxygen decreases and the dissociation curve shifts right
Where is the main respiratory centre that controls the rhythm of breathing?
Correct answer B. Medulla oblongata
Under normal conditions, which change in the blood is the strongest stimulus for increasing the rate of breathing?
Correct answer B. A rise in carbon dioxide (H⁺) concentration
Where are the peripheral chemoreceptors that monitor blood gases located?
Correct answer B. In the carotid and aortic bodies
Why does oxygen move from the alveoli into the blood of pulmonary capillaries?
Correct answer C. The partial pressure of oxygen in alveolar air is higher than in the blood
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What is the main damage caused to the lungs in emphysema?
Correct answer C. Breakdown of alveolar walls, reducing surface area and elasticity
Why do long-term smokers develop a persistent smoker’s cough?
Correct answer A. Tar and smoke damage cilia, so mucus collects and must be coughed up
Which component of tobacco smoke is mainly responsible for addiction and raises heart rate and blood pressure?
Correct answer D. Nicotine
Why is the oxygen dissociation curve of haemoglobin S-shaped (sigmoid)?
Correct answer B. Binding of one oxygen molecule makes it easier for the next ones to bind
Chronic bronchitis is mainly characterised by which change?
Correct answer B. Inflamed bronchi with excess mucus production and persistent coughing
During an asthma attack, why does breathing become difficult?
Correct answer B. Smooth muscle in bronchiole walls contracts and the airways narrow
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Which organism causes pulmonary tuberculosis?
Correct answer B. Mycobacterium tuberculosis
Which is a function of the nasal cavity in breathing?
Correct answer B. Filtering, warming and moistening the inhaled air
How do the walls of bronchioles differ from those of the trachea?
Correct answer C. Bronchioles lack cartilage and have smooth muscle in their walls
Which sequence shows the correct path of inhaled air?
Correct answer C. Nasal cavity → pharynx → larynx → trachea → bronchi → bronchioles → alveoli
At a resting tissue, haemoglobin falls from about 98% to 75% saturation. What fraction of the oxygen it carried has been unloaded?
Correct answer C. About one quarter
About Respiration and Gaseous Exchange MCQs
Questions trace the path of air through the nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles and alveoli, asking about the role of each part, the epiglottis, cartilage rings and ciliated epithelium. Breathing questions cover the action of the diaphragm and intercostal muscles, lung volumes and capacities, and the control of breathing by carbon dioxide levels. Gas exchange questions examine the features of alveoli, surfactant and diffusion. Transport questions cover haemoglobin, the oxygen dissociation curve, foetal haemoglobin, carbonic anhydrase and carbon monoxide poisoning. The final area deals with the effects of smoking, including chronic bronchitis, emphysema and lung cancer.
Key facts to remember
- Gas exchange takes place across the thin walls of the alveoli by diffusion.
- The trachea is kept open by C-shaped rings of cartilage.
- During inspiration the diaphragm contracts and flattens and the external intercostal muscles raise the ribs.
- Residual volume cannot be measured with a simple spirometer because it never leaves the lungs.
- Carbon monoxide binds to haemoglobin far more strongly than oxygen, reducing the blood's oxygen-carrying capacity.
- Most carbon dioxide is carried in the blood plasma as hydrogencarbonate (bicarbonate) ions.
Exams that include Respiration and Gaseous Exchange MCQs
Pakistan
- MDCAT
- NUMS
- AKU
- FSc boards
India
- NEET
Bangladesh
- HSC
- Medical Admission Test
How to prepare for Respiration and Gaseous Exchange MCQs
- Draw and label the respiratory tract from the nose to the alveoli and note one function for each part.
- Practise lung volume calculations, remembering that vital capacity equals tidal volume plus both reserve volumes.
- Sketch the oxygen dissociation curve and show how it shifts with more carbon dioxide and for foetal haemoglobin.
- Make a list of the effects of smoking, matching each substance in smoke to the damage it causes.
Frequently asked questions
Which exams ask Respiration MCQs?
In Pakistan, Respiration questions appear in MDCAT, the NUMS and AKU entry tests and FSc board papers. Students in India meet the same content in NEET, and in Bangladesh it is tested in HSC Biology and the Medical Admission Test.
How does smoking damage the respiratory system?
Tar in smoke paralyses and destroys cilia and increases mucus, causing smoker's cough and chronic bronchitis. Damage to alveolar walls leads to emphysema, carcinogens in tar can cause lung cancer, and carbon monoxide reduces how much oxygen the blood can carry.
Why are alveoli efficient at gas exchange?
Alveoli provide a huge surface area, have walls only one cell thick, are moist and are surrounded by a dense network of capillaries. Continuous blood flow and ventilation keep steep concentration gradients of oxygen and carbon dioxide, so diffusion is rapid.
Last reviewed October 2026