Question 1: Define diffusion in the context of cell biology.

Answer: Diffusion is the passive movement of particles from an area of higher concentration to an area of lower concentration until equilibrium is reached.

Question 2: Explain why diffusion is considered a passive process and does not require energy.

Answer: Because diffusion occurs due to the natural random movement of particles and does not require energy input from the cell.

Question 1: A gas diffuses across a membrane at a rate of 0.5 cm per minute over a distance of 10 cm. Calculate the time taken for the gas to diffuse completely across this distance.

Answer: Time = Distance / Rate = 10 cm / 0.5 cm per minute = 20 minutes.

Question 2: Using Fick's Law, if the surface area of a membrane is doubled, how does this affect the rate of diffusion, assuming all other factors remain constant?

Answer: The rate of diffusion doubles because the rate is directly proportional to the surface area.

Question 1: Describe a simple experiment to demonstrate diffusion of a dye in water. Include the variables you would control and safety precautions.

Answer: A piece of coloured dye is placed in a container of water at room temperature. The dye spreads out gradually, demonstrating diffusion. Variables to control include temperature, volume of water, and concentration of dye. Safety precautions involve handling dyes carefully to avoid staining and ensuring good ventilation if using chemicals.

Question 1: In an experiment, sodium chloride diffuses into a solution over 30 minutes, increasing its concentration from 0.1 mol/L to 0.4 mol/L. Explain what this data indicates about the direction of diffusion and the concentration gradient.

Answer: The increase in sodium chloride concentration indicates diffusion is occurring from an area of higher concentration (outside) into the solution, following the concentration gradient from high to low.

Question 1: Explain how diffusion is important in the process of gas exchange in the alveoli of the lungs.

Answer: Diffusion allows oxygen to move from the alveoli, where its concentration is high, into the blood, where its concentration is lower. Conversely, carbon dioxide diffuses from the blood into the alveoli to be exhaled, facilitating efficient gas exchange.

Question 2: Identify one technological application that utilises diffusion and briefly describe how it works.

Answer: Gas diffusion in dialysis machines allows waste products to pass from the blood into a dialysis fluid across a semi-permeable membrane, helping to clean the blood of patients with kidney failure.