Question 1: Gas exchange in the respiratory system involves the diffusion of oxygen into the blood and carbon dioxide out of the blood across the alveolar membrane. This process relies on differences in gas concentrations between the alveoli and the blood.

Answer: Gas exchange occurs through diffusion, driven by concentration gradients of oxygen and carbon dioxide between alveolar air and blood.

Question 2: Define 'diffusion' in the context of gas exchange in the lungs.

Answer: Diffusion is the passive movement of gas molecules from an area of higher concentration to an area of lower concentration across a semi-permeable membrane.

Question 1: Describe the role of alveoli in the process of gas exchange.

Answer: Alveoli provide a large surface area and a thin membrane that facilitates efficient diffusion of oxygen into the blood and carbon dioxide out of the blood.

Question 2: Explain why a rich blood supply is essential for effective gas exchange in the lungs.

Answer: A rich blood supply maintains a concentration gradient by removing oxygen and bringing in carbon dioxide, thus enabling continuous diffusion.

Question 1: Calculate the volume of oxygen absorbed by the blood if 250 ml of air containing 21% oxygen is involved in gas exchange. Assume all oxygen in the air is absorbed.

Answer: 52.5 ml

Question 2: If the partial pressure of carbon dioxide in alveolar air is 40 kPa and in deoxygenated blood is 45 kPa, in which direction will CO2 diffuse?

Answer: CO2 will diffuse from blood to alveolar air because its partial pressure is higher in the blood.

Question 1: Describe a safe way to investigate the effect of exercise on breathing rate in humans.

Answer: Participants can be asked to perform moderate exercise, with their breathing rate measured before and after, ensuring they rest between trials and are supervised for safety.

Question 2: Explain how understanding gas exchange can improve treatments for respiratory diseases such as COPD.

Answer: Understanding gas exchange mechanisms can help develop targeted therapies, improve oxygen therapy, and design better ventilators, leading to enhanced management of diseases like COPD which impair alveolar function.

Question 1: A patient with a lung capacity of 4 litres shows a reduced efficiency in gas exchange. Explain possible reasons for this reduction.

Answer: Possible reasons include damaged alveoli (as in emphysema), thickened alveolar walls (as in fibrosis), or reduced blood flow, all impairing diffusion.

Question 2: In a scenario where the concentration of oxygen in alveolar air decreases, predict how this affects the rate of oxygen absorption into the blood.

Answer: The rate of oxygen absorption will decrease because the concentration gradient driving diffusion is reduced.