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.