Gas exchange — AS & A Level Biology (9700) questions by topic
Airway tissue identification and gas-exchange surface adaptations sit at the centre of this topic: distinguishing a bronchiole from a bronchus in a photomicrograph, explaining smooth muscle's role in adjusting airway diameter, and counting the membranes an oxygen molecule crosses between alveolus and red blood cell. Identify, explain and describe lead the command words, and explain wants the tissue's actual mechanism, not just its name.
This set has 53 real questions from 2023 to 2025 papers, worth 1 to 18 marks, so single-tissue identification sits beside multi-part gas-exchange explanations. Submitting each answer for instant marking helps here, since confusing a bronchiole with a bronchus, or miscounting membranes crossed by oxygen, is flagged immediately rather than repeated.
What examiners look for
- A recurring error mistakes a bronchiole photomicrograph for a bronchus, and misattributes tissue P's function to support rather than airway diameter control.
- Goblet cells are commonly, and wrongly, included among the tissues present in a bronchus in this context.
- Smooth muscle's role is often confused with elastic tissue's stretch and recoil, or wrongly described as the bronchus itself contracting.
- Membrane drawings sometimes show a single phospholipid layer, or three fatty acid tails, rather than the correct bilayer with two tails.
- Strong answers correctly count five membranes crossed by an oxygen molecule between alveolus and red blood cell, and recognise smooth muscle contraction in the bronchus wall as the mechanism controlling diameter.
May–June 2025, Paper 11
How many times must an oxygen molecule pass through a cell surface membrane to get from the air in the alveolus to the haemoglobin in a red blood cell? (Assume there are no pores…
Answer this question and get it marked →Asthma can affect children and adults. The air passages become narrower, severely restricting the flow of air into the lungs. Salbutamol is a drug that widens the air passages to…
Answer this question and get it marked →The photomicrograph shows the transverse section of part of the trachea. Which letter represents a tissue that can contract and relax to adjust the diameter of the airways? A A B…
Answer this question and get it marked →May–June 2025, Paper 12
Which row shows the tissues that are present in the wall of the trachea and the wall of the bronchus? cartilage ciliated epithelium smooth muscle --- --- --- --- A ✓ ✓ ✓ B ✓ ✓ ✗ C…
Answer this question and get it marked →Which factors maintain the diffusion gradient for carbon dioxide at the surface of the alveoli? 1 blood flow around the alveoli 2 breathing movement exchanging air in the lungs 3…
Answer this question and get it marked →May–June 2025, Paper 13
Label Q on a diagram of the bronchiole indicates smooth muscle. What is the function of structure Q? A To produce mucus to trap pathogens. B To transport mucus towards the…
Answer this question and get it marked →Which feature maintains a steep diffusion gradient in the alveoli? A thick walls of the alveoli B the presence of mucus in the alveoli C high concentration of oxygen in the air…
Answer this question and get it marked →May–June 2025, Paper 14
Which reaction is catalysed by carbonic anhydrase? A the dissociation of carbonic acid B the formation of carbaminohaemoglobin C the formation of hydrogencarbonate ions and…
Answer this question and get it marked →What directly causes the percentage oxygen saturation of haemoglobin to decrease in actively respiring muscles? A hydrogencarbonate ions B carbon dioxide C carbonic acid D…
Answer this question and get it marked →Which row shows the tissues that are present in the wall of the trachea and also the wall of the bronchus? ciliated epithelium squamous epithelium smooth muscle --- --- --- --- A…
Answer this question and get it marked →May–June 2025, Paper 24
The human gas exchange system is responsible for the efficient uptake of oxygen into the blood and for the excretion of carbon dioxide. Ciliated epithelium is a lining tissue…
Answer this question and get it marked →May–June 2025, Paper 38
M1 is a slide of a stained transverse section through a leaf. Draw a large plan diagram of the region of the leaf on M1 indicated by the shaded area in Fig. 2.1 (the…
Answer this question and get it marked →May–June 2024, Paper 11
How are alveoli adapted to their function?
Answer this question and get it marked →The diagram shows oxygen diffusing from the space inside an alveolus into the blood through the gaseous exchange surface. W is the oxygen concentration in the blood; X is the…
Answer this question and get it marked →Which tissues are present in a bronchus? The columns are cartilage, ciliated epithelium and smooth muscle (key: tick = present, cross = not present).
Answer this question and get it marked →Steep concentration gradients must be maintained for efficient gaseous exchange to occur in the human lungs. Which row correctly describes how steep concentration gradients can be…
Answer this question and get it marked →May–June 2024, Paper 12
In the lungs, movement of dissolved carbon dioxide out of the capillaries occurs in one of two ways: by diffusion through the endothelial cells of the capillaries; or by leakage…
Answer this question and get it marked →What maintains the steep concentration gradients needed for successful gas exchange in the lungs? (1) Air flow in the alveoli is in the opposite direction to blood flow in the…
Answer this question and get it marked →Where is cartilage tissue always found in the human gas exchange system?
Answer this question and get it marked →Scientists compared the density of goblet cells in the lungs and the density of mucus in the lungs of three groups of people: people who do not smoke and do not have lung disease;…
Answer this question and get it marked →May–June 2024, Paper 13
Which structure of the gas exchange system always contains cartilage? A alveoli B bronchiole C capillary D bronchus
Answer this question and get it marked →Exchange of carbon dioxide and oxygen occurs between air in the alveoli and blood in the capillaries of the lung. Which partial pressures of the gases will allow gaseous exchange…
Answer this question and get it marked →The plan diagram shows a cross-section of a trachea. The plan diagram shows concentric layers of a trachea cross-section. Four labels point to different tissue layers: A points to…
Answer this question and get it marked →Which layers of cells does an oxygen molecule diffuse through when moving from an alveolus into an alveolar capillary? alveolus alveolar capillary --- --- --- A squamous…
Answer this question and get it marked →May–June 2024, Paper 21
Fig. 4.1 is a scanning electron micrograph showing the tissue that lines the bronchi in the gas exchange system (magnification x3000). Fig. 4.2 is a transmission electron…
Answer this question and get it marked →May–June 2024, Paper 22
Smooth muscle is a tissue composed of smooth muscle cells. The cells contain cytoplasm packed with proteins that are involved in contraction and relaxation. Smooth muscle is…
Answer this question and get it marked →October–November 2024, Paper 11
What is the function of cilia in the gas exchange system?
Answer this question and get it marked →Which tissues are present in the walls of a trachea and an alveolus? Row structure epithelium with goblet cells smooth muscle --- --- --- --- A trachea present present A alveolus…
Answer this question and get it marked →The photomicrograph shows part of a bronchus, with four structures labelled A, B, C and D. Label D points to the ciliated epithelium at the inner surface; label C points to a band…
Answer this question and get it marked →October–November 2024, Paper 12
Which row shows the features of the gas exchange surface that increase diffusion of carbon dioxide and oxygen? Row concentration gradient diffusion distance --- --- --- A steep…
Answer this question and get it marked →The electron micrograph shows some of the airways in the gaseous exchange system of an insect and the respiring body cells that surround them. Annotations note that each trachea…
Answer this question and get it marked →Which row is correct for the wall of the trachea and the wall of the bronchus? (The row applies to both the trachea and the bronchus.) Row cartilage smooth muscle goblet cells ---…
Answer this question and get it marked →October–November 2024, Paper 13
Which structures are present in the trachea and also in all bronchioles? 1 cartilage; 2 smooth muscle; 3 epithelial cells.
Answer this question and get it marked →The photomicrograph shows a section through part of the gas exchange system. It shows numerous small thin-walled air sacs (alveoli) with a flattened squamous epithelium. Which…
Answer this question and get it marked →What is the function of the goblet cells in the gas exchange system?
Answer this question and get it marked →October–November 2024, Paper 21
Fig. 3.1 is a photomicrograph of a transverse section through a region of the wall of the bronchus in the gas exchange system. Tissue J is a pale region containing rounded cells…
Answer this question and get it marked →October–November 2024, Paper 23
Fig. 1.1 shows the structure of the human gas exchange system, with parts labelled A (larynx region), B, C (lung), D, E, F, G (bronchiole/alveoli region) by lines pointing to…
Answer this question and get it marked →May–June 2023, Paper 11
A person with no breathing conditions rests for an hour. Their breathing in this time is shallow and slow, so little air from outside the body reaches the alveoli. The person's…
Answer this question and get it marked →Which statements about all bronchioles are correct? 1 They have epithelium. 2 They have goblet cells. 3 They have muscle tissue. A 1, 2 and 3 B 1 and 3 only C 2 only D 3 only
Answer this question and get it marked →May–June 2023, Paper 12
Where are squamous epithelial cells found in the human gas exchange system? The options are given as a table with a tick for 'found' and a cross for 'not found' across trachea,…
Answer this question and get it marked →Which statement about gas exchange between air in the alveoli and blood in the pulmonary capillaries is correct? A The oxygen concentration in the capillaries leaving the…
Answer this question and get it marked →The average thicknesses for some structures in the human respiratory system are shown. structure average thickness of structure /nm --- --- human cell membrane 5 cytoplasm of…
Answer this question and get it marked →May–June 2023, Paper 13
The photomicrograph shows a part of the human gas exchange system with one tissue labelled P, surrounding a small folded lumen. Which row is correct? A part of gas exchange system…
Answer this question and get it marked →How many times must a molecule of oxygen pass through a cell surface membrane as it diffuses from the airspace inside an alveolus, through a cell in the capillary wall, to bind to…
Answer this question and get it marked →May–June 2023, Paper 22
The Weibel Lung model was developed after an extensive study of the gas exchange system. The model includes detailed measurements of airway diameters (lumen diameters of the…
Answer this question and get it marked →October–November 2023, Paper 11
Oxygen and carbon dioxide enter and leave the blood in the capillaries of the alveoli. Which statement about this process is correct? A Oxygen and carbon dioxide only pass through…
Answer this question and get it marked →October–November 2023, Paper 12
Which statements about all bronchioles are correct? 1 They have goblet cells. 2 They have epithelial cells. 3 They have muscle tissue. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D…
Answer this question and get it marked →The electron micrograph shows tissue at x850 magnification. What is shown in the electron micrograph? A scanning electron micrograph of bronchial epithelium and lymphocytes B…
Answer this question and get it marked →October–November 2023, Paper 13
What is typically found in the trachea, bronchi and bronchioles in the human gas exchange system? A cartilage B ciliated epithelium C squamous epithelium D squamous endothelium
Answer this question and get it marked →The photomicrograph shows a section through part of the human gas exchange system. Which structure is shown? A alveolus B bronchiole C bronchus D trachea
Answer this question and get it marked →Which factors are required for the efficient diffusion of oxygen and carbon dioxide in the human gas exchange system? 1 clean and warm air entering the lungs 2 maximised area of…
Answer this question and get it marked →October–November 2023, Paper 21
Fig. 5.1 is a photomicrograph of a transverse section of a bronchus in the lungs. The tissue labelled smooth muscle and the tissue labelled T are shown. Identify the tissue…
Answer this question and get it marked →October–November 2023, Paper 22
The alveoli of the lungs are the main gas exchange surface in humans. Explain how blood flow through the alveolar capillaries helps to maintain steep diffusion gradients for gas…
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