Grade 10 biology – Gaseous Exchange and Respiration Quiz
1. What is the main function of the respiratory system in animals?
The primary role of the respiratory system is gas exchange: supplying oxygen to the blood for cellular respiration and removing carbon dioxide, a metabolic waste.
2. In mammals, where does most gaseous exchange occur?
Alveoli are tiny air sacs with very thin walls and large surface area, specialised for rapid diffusion of oxygen and carbon dioxide between air and blood.
3. How do fish gills maintain efficient oxygen uptake from water?
Countercurrent flow keeps a gradient along the gill lamellae so blood encounters water with progressively higher oxygen, maximising diffusion into blood.
4. How do insects primarily deliver oxygen to their body cells?
Insects use tracheae and tracheoles that carry air directly to cells, so oxygen does not rely on the circulatory system for delivery.
5. Which respiratory surface is especially important for gas exchange in many amphibians?
Many amphibians (e.g., frogs) exchange gases through moist skin as well as lungs; the skin must stay moist to allow diffusion of gases.
6. What is the role of the diaphragm during inhalation in humans?
When the diaphragm contracts it flattens and moves downward, increasing chest cavity volume and causing air to flow into the lungs.
7. What is the function of pleural fluid between the lung membranes?
Pleural fluid lubricates the pleural surfaces so the lungs can expand and recoil smoothly during breathing.
8. Which substance carries most oxygen in human blood?
Haemoglobin binds oxygen in red blood cells and transports the majority of oxygen from lungs to tissues; only a small amount is dissolved in plasma.
9. During exercise, breathing rate increases mainly because:
Increased muscle activity raises CO2 and H+ levels; central and peripheral chemoreceptors detect these changes and increase breathing to remove CO2 and supply more oxygen.
10. What creates the driving force for diffusion of oxygen from air into blood at the respiratory surface?
Gases diffuse from areas of higher partial pressure to lower partial pressure; oxygen moves from alveolar air (higher pO2) into blood (lower pO2).
11. Which of the following is an adaptation of alveoli for efficient gas exchange?
Alveoli provide a huge surface area and thin (one-cell-thick) walls to shorten diffusion distance and speed up gas exchange.
12. Why does countercurrent flow in fish gills result in more oxygen uptake than parallel flow?
Countercurrent flow keeps blood encountering water with higher oxygen, maintaining diffusion gradient across the whole surface and maximising uptake.
13. Which tiny structures increase the surface area of fish gills where gas exchange occurs?
Gill filaments have many thin lamellae which provide a large surface area and short diffusion distance for oxygen to enter blood.
14. What is the role of surfactant in mammalian lungs?
Surfactant reduces surface tension of the thin fluid lining alveoli, preventing collapse (atelectasis) and making breathing easier.
15. Which muscles, besides the diaphragm, help expand the chest during deep inhalation?
External intercostal muscles contract to lift and expand the ribcage, increasing thoracic volume during inspiration.
16. What is vital capacity?
Vital capacity is the total usable lung volume (max inspiration followed by max expiration) and is commonly measured in respiratory tests.
17. How is most carbon dioxide transported in blood from tissues to lungs?
CO2 reacts with water to form carbonic acid, which dissociates to bicarbonate; most CO2 is transported this way in plasma after conversion in red blood cells.
18. What danger does carbon monoxide (CO) pose to oxygen transport in blood?
Carbon monoxide has a high affinity for haemoglobin and forms carboxyhaemoglobin, blocking oxygen binding and reducing oxygen delivery to tissues.
19. Which factor shifts the oxygen-haemoglobin dissociation curve to the right (Bohr effect), making haemoglobin release more oxygen to tissues?
Higher temperature, more CO2 and increased acidity reduce haemoglobin's affinity for oxygen, promoting O2 release to active tissues (Bohr effect).
20. What is a likely effect of cigarette smoke on the respiratory system?
Smoke damages the cilia in airways, so mucus cannot be cleared effectively, increasing infection risk and reducing airflow and gas exchange.
21. Why is oxygen less available in water than in air, affecting aquatic animals?
Water holds less dissolved oxygen and diffusion is slower, so aquatic animals have specialised gills and ventilatory adaptations to extract enough oxygen.
22. Which statement best describes the mechanism of gas exchange across respiratory surfaces?
Gases move by diffusion from regions of higher partial pressure to lower partial pressure across thin, moist respiratory surfaces.
23. In human lungs, where are exchange surfaces kept moist and thin to allow diffusion?
Alveolar epithelium is extremely thin and covered by a small amount of fluid with surfactant to permit gas diffusion while preventing collapse.
24. Which animal group uses positive pressure ventilation by forcing air into lungs (buccal pumping) rather than negative pressure like mammals?
Many amphibians use buccal pumping: they push air into their lungs using movements of the mouth floor (positive pressure), unlike the negative pressure breathing of mammals.
25. What role do chemoreceptors play in breathing control?
Chemoreceptors in the carotid bodies and brainstem sense changes in CO2, O2 and pH and send signals to adjust rate and depth of breathing to maintain homeostasis.
26. Where does the main gaseous exchange take place in the human respiratory system?
Alveoli are tiny air sacs with very thin walls, large surface area and rich blood supply, which allow oxygen and carbon dioxide to diffuse rapidly between air and blood.
27. Which structure allows fish to extract oxygen from water?
Gills have thin filaments and many lamellae that provide a large surface area and use countercurrent flow to absorb dissolved oxygen from water into the blood.
28. How do most insects carry oxygen to their body cells?
Insects have a tracheal system: air enters via spiracles and moves through branching tracheae and tracheoles directly to cells, allowing gas exchange by diffusion without using the blood to transport oxygen.
29. What happens to the diaphragm during inhalation in humans?
When the diaphragm contracts it flattens and the chest cavity expands, lowering internal pressure and drawing air into the lungs.
30. What is the primary function of haemoglobin in blood?
Haemoglobin in red blood cells binds oxygen in the lungs and releases it in tissues where it is needed for respiration.
31. Which principle explains the movement of oxygen from the alveoli into the blood?
Diffusion is driven by partial pressure gradients: oxygen has higher partial pressure in alveolar air than in blood, so it diffuses into the blood.
32. Which adaptation of alveoli most increases the rate of gas exchange?
Alveoli are numerous and small, providing a very large total surface area for diffusion which increases the rate of gas exchange.
33. What feature of the bird respiratory system improves efficiency of gas exchange compared to mammals?
Birds have air sacs that produce a continuous, one-way flow of air through the lungs, maintaining a higher and more constant oxygen gradient across the respiratory surface.
34. What is tidal volume?
Tidal volume is the amount of air moved in or out of the lungs during a normal, resting breath.
35. Which gas must be removed from the body to avoid build-up and maintain normal blood pH?
Carbon dioxide produced by cellular respiration is carried to the lungs and exhaled; its removal prevents acidification of the blood and helps maintain pH balance.
36. What is the name of the effect where increased CO2 in tissues causes haemoglobin to release more oxygen?
The Bohr effect describes how an increase in carbon dioxide (or lower pH) reduces haemoglobin's affinity for oxygen, promoting oxygen release to active tissues.
37. Which pigment carries oxygen in human blood?
Haemoglobin is the iron-containing protein in red blood cells responsible for transporting oxygen; chlorophyll is in plants and hemocyanin occurs in some invertebrates.
38. Why are smokers more likely to get chest infections?
Cilia sweep mucus and trapped microbes out of the airways; smoking destroys cilia function, allowing mucus and pathogens to build up and cause infections.
39. Which structure prevents food from entering the trachea during swallowing?
The epiglottis is a flap of tissue that closes the glottis during swallowing, directing food into the oesophagus and preventing it from entering the trachea.
40. Most oxygen in the blood is transported in which form?
About 98% of oxygen is carried bound to haemoglobin; only a small fraction is dissolved directly in the plasma.
41. How is most carbon dioxide transported from tissues to the lungs?
CO2 enters red blood cells, is converted to bicarbonate by carbonic anhydrase, and most bicarbonate diffuses into plasma for transport to the lungs.
42. Which change occurs in emphysema that reduces efficiency of gas exchange?
Emphysema destroys alveolar walls and reduces total respiratory surface area, which decreases the rate of oxygen and carbon dioxide exchange.
43. What is the function of pleural fluid in the chest cavity?
Pleural fluid lubricates the pleural surfaces so the lungs can expand and contract smoothly within the chest during breathing.
44. What does vital capacity measure?
Vital capacity is the greatest volume of air a person can expel after taking the deepest possible breath and is used to assess lung function.
45. In amphibians such as frogs, where does gaseous exchange occur besides the lungs?
Many amphibians have thin, moist skin rich in blood vessels that allows oxygen and carbon dioxide to diffuse directly between the environment and the blood.
46. At the end of the insect tracheoles gas exchange occurs by which process?
Tracheoles end close to individual cells, and gases move by diffusion across the thin tracheolar walls into cells, so the insect's circulatory fluid is not required to carry oxygen.
47. Why is countercurrent flow important in fish gills?
Countercurrent flow means water and blood flow in opposite directions across the gill lamellae, keeping the oxygen gradient along the entire surface and maximising oxygen uptake.
48. What immediate effect does hyperventilation have on blood gases and pH?
Rapid breathing expels CO2 faster than it is produced, reducing carbonic acid in blood and causing a temporary rise in pH (respiratory alkalosis), which can cause dizziness.
49. How many cell layers thick are alveolar walls to allow efficient gas exchange?
Alveolar walls are made of a single thin layer of squamous epithelial cells to minimize diffusion distance and speed up gas exchange.
50. What is the main chemical stimulus detected by chemoreceptors that increases breathing rate?
Chemoreceptors in the medulla and carotid bodies respond primarily to increased CO2 (and lower pH) by stimulating faster and deeper breathing to remove excess CO2.