Question 1: Define the term 'gas exchange' as it occurs in the human respiratory system.

Answer: Gas exchange is the process by which oxygen is absorbed into the blood and carbon dioxide is removed from it in the lungs.

Question 2: Explain how the structure of alveoli facilitates efficient gas exchange.

Answer: Alveoli have a large surface area, thin walls, and are surrounded by numerous capillaries, which together enable efficient diffusion of gases between the lungs and blood.

Question 3: Calculate the volume of oxygen (in litres) absorbed by a person breathing 15 times per minute, each breath taking in 0.5 litres of air, if the oxygen concentration in inspired air is 21% and in expired air is 16%.

Answer: Step 1: Calculate inspired oxygen per breath: 0.5 L × 0.21 = 0.105 L Step 2: Calculate expired oxygen per breath: 0.5 L × 0.16 = 0.08 L Step 3: Oxygen absorbed per breath: 0.105 L – 0.08 L = 0.025 L Step 4: Total oxygen absorbed per minute: 0.025 L × 15 breaths = 0.375 L

Question 4: Identify two factors that can increase the efficiency of gas exchange in the lungs.

Answer: Increased surface area of alveoli and greater blood flow around the alveoli.

Question 5: Describe a simple experiment to investigate the effect of exercise on breathing rate.

Answer: Students can measure their resting breathing rate, then perform moderate exercise, such as jogging in place for a set period, and measure their breathing rate immediately after. Variables include exercise intensity (independent), breathing rate (dependent), and environmental conditions (controlled). Safety precautions include warming up beforehand and avoiding overexertion.

Question 6: A patient’s exhaled air contains 16% oxygen and 4% carbon dioxide. Explain what this indicates about gas exchange efficiency.

Answer: It indicates that oxygen has been absorbed into the blood and carbon dioxide has been removed efficiently during gas exchange.

Question 7: Fill in the blank: During gas exchange, oxygen diffuses from the alveoli into the blood because the concentration of oxygen is higher in the _____ than in the blood.

Answer: alveoli

Question 8: Explain the role of haemoglobin in gas exchange.

Answer: Haemoglobin is a protein in red blood cells that binds to oxygen, allowing efficient transport of oxygen from the lungs to body tissues and aiding in the removal of carbon dioxide from tissues back to the lungs.

Question 9: Which of the following best describes the process of gas exchange in the alveoli? A) Active transport of gases B) Diffusion of gases due to concentration gradients C) Osmosis of gases D) Filtration of gases

Answer: B) Diffusion of gases due to concentration gradients

Question 10: Identify the main environmental factor that can impair gas exchange in the lungs and explain its effect.

Answer: Air pollution, such as pollutants or particulates, can damage alveoli and reduce their surface area, impairing gas exchange efficiency.

Question 11: Discuss how the respiratory system adapts during strenuous physical activity to meet increased oxygen demands.

Answer: During strenuous activity, the respiratory system increases breathing rate and depth to enhance oxygen intake and carbon dioxide removal. The heart rate also increases to circulate oxygenated blood more rapidly, and alveoli may expand to facilitate greater gas exchange. These adaptations help meet the higher metabolic demands of muscles.