Grade 10 general science – Respiration Quiz
1. Which gas do human lungs take in for use by body cells during respiration?
Oxygen is inhaled into the lungs and transported by the blood to cells where it is used in aerobic respiration to release energy from food.
2. Where does most gas exchange between air and blood occur in the human respiratory system?
Alveoli are tiny air sacs with very thin walls and lots of capillaries, giving a large surface area for oxygen and carbon dioxide to diffuse between air and blood.
3. Which muscle contracts and moves downwards to increase chest volume during inhalation?
The diaphragm contracts and flattens during inhalation, increasing thoracic volume and allowing air to be drawn into the lungs.
4. What is the name of the process by which cells release energy from food using oxygen?
Aerobic respiration uses oxygen to fully break down glucose into carbon dioxide and water, releasing large amounts of energy for the cell.
5. Which of the following correctly describes the simplified word equation for aerobic respiration?
In aerobic respiration glucose reacts with oxygen to produce carbon dioxide and water and to release energy stored in the glucose molecules.
6. During vigorous exercise when oxygen is limited, human muscle cells carry out anaerobic respiration producing:
When oxygen is in short supply, muscle cells convert glucose to lactic acid (lactate) to release some energy, which can cause muscle fatigue and cramps.
7. When yeast performs anaerobic respiration (fermentation), what are the main products?
Yeast ferments glucose to produce ethanol and carbon dioxide; the CO2 causes bread to rise and ethanol is used in brewing.
8. Which body system transports oxygen from the lungs to the rest of the body?
The circulatory system (heart and blood vessels) carries oxygen in the blood from the lungs to body cells and returns carbon dioxide to the lungs.
9. Which structure closes over the windpipe when we swallow to prevent food entering the lungs?
The epiglottis is a flap of tissue that covers the trachea during swallowing, directing food to the oesophagus and protecting the airway.
10. During inhalation the diaphragm contracts and moves in which direction?
When the diaphragm contracts it flattens and moves downward, increasing the volume of the chest cavity and drawing air into the lungs.
11. Which component of blood carries most of the oxygen around the body?
Haemoglobin, a protein in red blood cells, binds oxygen in the lungs and releases it to tissues, carrying far more oxygen than plasma alone.
12. How is most carbon dioxide transported in the blood from tissues to the lungs?
Most CO2 reacts with water in red blood cells to form bicarbonate ions (HCO3−), which are transported in plasma to the lungs where CO2 is released.
13. Which respiratory condition is characterised by permanent destruction of alveoli and reduced surface area for gas exchange?
Emphysema (often linked to smoking) destroys alveolar walls, reducing the surface area for gas exchange and causing breathlessness.
14. Where on a leaf does most gas exchange (oxygen and carbon dioxide) with the air occur?
Stomata are pores on the leaf surface that open and close to allow gases in and out for photosynthesis and respiration.
15. Compared with anaerobic respiration, aerobic respiration in cells produces:
Aerobic respiration fully breaks down glucose using oxygen and produces much more energy (ATP) per glucose molecule than anaerobic pathways.
16. What is the role of tiny hair-like cilia lining the trachea and bronchi?
Cilia beat in a coordinated way to push mucus loaded with dust and microbes upwards to the throat where it can be swallowed or expelled, keeping the lungs clear.
17. Why does breathing rate increase during physical exercise?
During exercise muscles respire faster, needing more oxygen and producing more CO2; breathing rate increases to meet oxygen demand and remove CO2.
18. Tuberculosis (TB), a common respiratory disease in Kenya, is caused by which type of organism?
TB is caused by the bacterium Mycobacterium tuberculosis and spreads through airborne droplets when an infected person coughs or sneezes.
19. Which simple action helps reduce spread of many respiratory infections in schools and at home?
Covering coughs and sneezes (with a tissue or elbow) reduces the number of infectious droplets released into the air, lowering transmission.
20. What is the function of the thin layer of pleural fluid between the lungs and chest wall?
Pleural fluid lubricates the surfaces of the lungs and chest wall so they glide smoothly during inhalation and exhalation.
21. Which gas is the main waste product expelled from the body during respiration?
Carbon dioxide is produced by cells during respiration and is carried by blood to the lungs to be exhaled as a waste product.
22. In which cell organelle does the majority of aerobic cellular respiration occur?
Mitochondria are the 'powerhouses' of the cell where the Krebs cycle and electron transport chain produce most of the ATP during aerobic respiration.
23. How does cigarette smoke affect the cilia in the airways?
Chemicals in smoke damage cilia, preventing them from clearing mucus and particles, which increases infection risk and contributes to chronic cough.
24. In a school experiment, which observation indicates carbon dioxide is being produced during respiration of a small animal or germinating seeds?
Carbon dioxide reacts with calcium hydroxide (limewater) to form calcium carbonate, which makes the solution cloudy or milky, showing CO2 is present.
25. What happens to a person's breathing rate when they have a fever?
Fever raises the body's metabolic rate, so cells use more oxygen and produce more CO2, causing an increase in breathing rate to meet demand.
26. What is the main difference between breathing and respiration?
Breathing (ventilation) is a physical movement of air; respiration refers to biochemical processes (like glycolysis and aerobic respiration) that break down food to release energy (ATP).
27. Which structure is the primary site of gaseous exchange in the human lungs?
Alveoli are tiny air sacs with thin walls and a large surface area where oxygen diffuses into blood and carbon dioxide diffuses out.
28. Which muscle contracts to increase the volume of the thoracic cavity during inhalation?
Contraction of the diaphragm flattens it, increasing thoracic volume and causing air to be drawn into the lungs during inhalation.
29. Which of the following best describes the path of air from the outside to the alveoli?
Air enters through the nose, passes pharynx and larynx into the trachea, which branches into bronchi and bronchioles that end in alveoli.
30. What approximate percentage of oxygen is present in inhaled atmospheric air at sea level?
Atmospheric air at sea level contains about 21% oxygen, about 78% nitrogen and small amounts of other gases.
31. Why does oxygen move from alveolar air into the blood?
Gases move by diffusion from regions of higher partial pressure to lower partial pressure; alveolar oxygen partial pressure is higher than in deoxygenated blood.
32. How is most oxygen transported in human blood?
About 97% of oxygen is carried bound to hemoglobin in red blood cells; only a small fraction is dissolved in plasma.
33. Which gas is mainly transported as bicarbonate ions in the blood?
Carbon dioxide is largely converted to bicarbonate ions (HCO3-) in red blood cells for transport in plasma before being expelled at the lungs.
34. During heavy exercise, muscle cells may produce energy anaerobically. What compound is commonly formed in human muscle during anaerobic respiration?
When oxygen is limited, muscles perform anaerobic respiration converting glucose to lactic acid, yielding small amounts of ATP.
35. Which process yields the most ATP per glucose molecule?
Aerobic respiration fully oxidises glucose in mitochondria (Krebs cycle + electron transport), producing much more ATP (~36–38) than anaerobic pathways.
36. What is vital capacity?
Vital capacity is the total usable lung volume measured by the largest breath in followed by the largest breath out.
37. Which of the following adaptations helps alveoli to be efficient at gas exchange?
Thin, moist walls and a large surface area with rich blood supply allow rapid diffusion of gases between air and blood.
38. Which statement correctly describes the role of hemoglobin in red blood cells?
Hemoglobin binds oxygen in the lungs and releases it in tissues; it also carries some CO2 as carbaminohemoglobin or facilitates bicarbonate formation.
39. What effect does smoking have on the respiratory system?
Smoke damages airway cilia, increases mucus production and can destroy alveolar walls, all reducing efficient gas exchange and increasing disease risk.
40. Which of the following best describes external respiration?
External respiration is gas exchange between the alveolar air and pulmonary blood; internal respiration refers to exchange at tissues.
41. How does carbon monoxide (CO) affect oxygen transport in blood?
CO binds tightly to hemoglobin's binding sites, reducing oxygen carriage and causing tissue hypoxia even if oxygen levels are normal.
42. What is the immediate energy-carrying molecule produced during cellular respiration that cells use for work?
ATP stores and supplies energy for cellular processes and is produced during cellular respiration from the breakdown of glucose.
43. Which of these processes occurs in mitochondria during aerobic respiration?
The Krebs cycle and electron transport chain take place in mitochondria and are central to aerobic ATP production.
44. Why does breathing rate increase at high altitude?
At high altitudes lower air pressure reduces oxygen partial pressure; the body increases breathing to raise oxygen uptake.
45. In plants, where does gaseous exchange mainly occur?
Plants exchange gases mainly via stomata in leaves and lenticels in stems, allowing CO2 in for photosynthesis and O2 out from respiration.
46. Which event causes air to move out of the lungs during normal quiet exhalation?
During quiet exhalation the diaphragm relaxes, thoracic volume decreases, intrapulmonary pressure rises and air is expelled passively.
47. What causes the red colour of oxygenated blood in arteries?
Oxygen binding to haemoglobin changes its shape and colour, making oxygenated arterial blood bright red.
48. Which condition is characterised by constricted airways and difficulty breathing, often triggered by allergens or exercise?
Asthma involves spasms of bronchioles, mucus production and airway narrowing causing wheezing and breathlessness; triggers include allergens and exercise.
49. What happens to lactic acid produced in muscles after strenuous exercise?
Lactic acid is transported to the liver where it can be converted back to glucose in the Cori cycle once oxygen is available.
50. Which measurement would a doctor use to assess how much air you normally breathe in a single relaxed breath?
Tidal volume is the amount of air inhaled or exhaled during a normal relaxed breath; other measures refer to maximum volumes or residual air.