39 past paper MCQs from Biology unit 13, Respiration, across 1 topic. They are arranged topic by topic; bigger topics show a sample here and link to their full set and to study notes. Tap “Show answer” for the correct option and a short solution.
1.Respiratory surfaces exhibit which characteristic? (MDCAT 2022)
Correct answer: (a) it must be permeable
Gases must pass through it, so it is thin, moist, permeable and richly supplied with blood.
2.Smooth muscles are found in all of the following except the: (MDCAT 2023)
Correct answer: (d) alveoli
The alveolar wall is one cell thick, for gas exchange, and carries no muscle.
3.The method of bringing oxygenated air into contact with a gas exchange surface is called: (MDCAT 2023)
Correct answer: (b) ventilation
Ventilation is the movement of the medium over the surface; respiration is what the cells then do with the oxygen.
4.About 70% of the carbon dioxide is carried in the blood as: (MDCAT 2024)
Correct answer: (b) bicarbonate
Most of it travels as hydrogen carbonate ions in the plasma.
5.The range of normal total lung capacity in humans is: (MDCAT 2024)
Correct answer: (a) 5-6 litres
Total lung capacity is about 5 to 6 litres in an adult.
6.The primary function of larynx is: (UHS MDCAT 2025)
Correct answer: (d) Voice production
The larynx carries the vocal cords, so it is the voice box.
7.Which of the following best describes Inspiratory Reserve Volume (IRV)? (KMU MDCAT 2025)
Correct answer: (d) The volume of air forcibly inhaled after normal tidal volume
The inspiratory reserve is the extra air that can still be drawn in after a normal breath.
8.During gaseous exchange in human respiration, enzyme carbonic anhydrase is directly involved in the: (KMU MDCAT 2025)
Correct answer: (b) Combination of water with carbon dioxide
Carbonic anhydrase of the red cell joins carbon dioxide to water to give carbonic acid.
9.What happens when the external intercostal muscles contract during inhalation in humans? (KMU MDCAT 2025)
Correct answer: (b) The ribs move outward
The external intercostals swing the ribs up and out, enlarging the chest.
10.The primary effect of smoking on the respiratory system: (KMU MDCAT 2025)
Correct answer: (c) Damage to alveoli reducing gaseous exchange
Smoke destroys the alveolar walls, so the surface left for gas exchange shrinks.
11.Which protein is present in the walls of alveoli? (NUMS MDCAT 2025)
Correct answer: (a) Collagen
The alveolar wall is a thin sheet of collagen and elastin fibres under the squamous epithelium.
12.The main function of the pharynx in respiratory system: (SIBA MDCAT 2025)
Correct answer: (a) Serves as passage for both food and air
The pharynx is the shared passage behind the mouth through which both food and air travel.
13.About 70% of the carbon dioxide is carried in blood as: (UHS MDCAT 2024)
Correct answer: (b) Bicarbonate
Most carbon dioxide is carried as hydrogen carbonate ions in the plasma.
14.Range of normal total lung capacity in humans is (UHS MDCAT 2024)
Correct answer: (a) 5-6 liter
Total lung capacity in an adult is about five to six litres.
15.Most CO2 in blood is transported as bicarbonate ions. Choose the event NOT taking place during gaseous exchange at tissue level: (NUMS MDCAT 2024)
Correct answer: (c) Formation of oxyhemoglobin
At the tissues oxyhaemoglobin is giving up its oxygen, not being formed.
16.The respiratory surfaces exhibit following characteristic? (UHS MDCAT 2023)
Correct answer: (a) It must be permeable
Gases must pass through it, so it is thin, moist and permeable.
17.The area between the two lungs is called: (SZABMU MDCAT 2023)
Correct answer: (c) Mediastinum
The space between the lungs, holding the heart and great vessels, is the mediastinum.
18.The percentage of CO2 carried as carboxyhemoglobin is? (PMC MDCAT 2022)
Correct answer: (c) 23
About $23\%$ of the carbon dioxide is carried bound to haemoglobin as carbamino-haemoglobin.
19.Which one is a contagious disease (PMC MDCAT 2022)
Correct answer: (c) pulmonary tuberculosis
Tuberculosis is spread from person to person in droplets; the other three are not caught.
20.Lungs are spongy due to the presence of million of? (PMC MDCAT 2022)
Correct answer: (a) Alveoli
The lungs are filled with millions of alveoli, which is what makes them spongy.
21.The following part is common in both the digestive system and respiratory systems of human beings (NUMS MDCAT 2022)
Correct answer: (b) Pharynx
The pharynx is the shared passage for food and for air.
22.Which of the following parts of the respiratory system has no cartilage? (NUMS MDCAT 2022)
Correct answer: (c) Bronchioles
The bronchioles have no cartilage rings, only smooth muscle in their walls.
23.The infection of lungs is called: (PMC Practice 2021)
Correct answer: (c) Pneumonia
Pneumonia is inflammation of the lungs, usually from infection.
24.Breathing is considered as a: (PMC Practice 2021)
Correct answer: (c) Mechanical process
Breathing is the muscular movement that ventilates the lungs, a mechanical process.
25.The voice box leads to the trachea which is also called (PMC Practice 2021)
Correct answer: (c) Windpipe
The trachea is commonly called the windpipe.
26.The structural and functional unit of the lungs is: (PMC Practice 2021)
Correct answer: (a) Alveoli
The alveolus is where the exchange of gases happens, so it is the functional unit.
27.During the transport of carbon dioxide, blood does not become acidic due to: (PMC Practice 2021)
Correct answer: (a) Blood buffer
The hydrogen carbonate and protein buffers of the blood take up the protons as they are formed.
28.A disease caused by gradual breakdown of the thin walls of alveoli is; (UHS MDCAT 2019)
Correct answer: (c) Emphysema
Emphysema is the breakdown of the alveolar walls, which cuts the surface for gas exchange.
29.During inspiration, the space inside the chest cavity is increased due to: (UHS MDCAT 2019)
Correct answer: (d) The contraction of the muscles of the diaphragm
The diaphragm contracts and flattens, which deepens the chest cavity.
30.Which of the following statements is correct about the respiratory pigments? (UHS MDCAT 2018)
Correct answer: (c) Myoglobin has more affinity for oxygen as compared to haemoglobin
Myoglobin holds oxygen more tightly than haemoglobin, so it takes it up in the muscle.
31.During breathing air from Pharynx enters to: (UHS MDCAT 2018)
Correct answer: (a) Trachea
Air passes from the pharynx through the larynx into the trachea.
32.The low levels of Surfactant produced by Alveolar epithelium causes: (UHS MDCAT 2018)
Correct answer: (a) Respiratory distress syndrome
Without surfactant the alveoli collapse at each breath out, which is respiratory distress syndrome.
33.Gradual breakdown of the alveolar wall leads to which type of disease in a smoker? (UHS MDCAT 2018)
Correct answer: (c) Emphysema
Emphysema is the destruction of the alveolar walls, which cuts the surface for gas exchange.
34.The site of gaseous exchange in humans is: (UHS MDCAT 2017)
Correct answer: (d) Alveoli
The alveoli are the thin walled sacs across which the gases pass.
35.The disease in which there is a breakdown of thin walls of alveoli: (UHS MDCAT 2017)
Correct answer: (b) Emphysema
Emphysema is the breakdown of the alveolar walls.
36.Gaseous exchange in animals takes place through: (UHS MDCAT 2017)
Correct answer: (c) Diffusion
Gases cross the respiratory surface by simple diffusion down their gradients.
37.The amount of CO2 exhaled from lungs during expiration is: (UHS MDCAT 2017)
Correct answer: (a) 4%
Exhaled air carries about four per cent carbon dioxide against $0.04\%$ in the air breathed in.
38.Breathing consists of: (UHS MDCAT 2016)
Correct answer: (d) Two phases
Breathing has two phases, inspiration and expiration.
39.Carboxyhaemoglobin (10-20%) is formed when CO2 combines with: (UHS MDCAT 2016)
Correct answer: (a) Amino group of haemoglobin
Carbon dioxide combines with the terminal amino groups of the globin chains.
Human Respiratory System notes →