Question 1: Define osmosis and explain its significance in plant and animal cells.

Answer: Osmosis is the movement of water molecules across a semi-permeable membrane from a region of lower solute concentration to a region of higher solute concentration. It is vital for maintaining cell turgor in plants and fluid balance in animals.

Question 2: Describe the mechanism by which water moves during osmosis at the cellular level.

Answer: Water moves through a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration, driven by differences in water potential, until equilibrium is reached.

Question 3: In an experiment, a plant cell is placed in a solution with a higher concentration of solutes than the cell’s cytoplasm. What is likely to happen to the cell?

Answer: The cell will lose water and become plasmolysed, shrinking as water moves out of the cell.

Question 4: Calculate the water potential difference if 2 litres of water move across a membrane from a solution with a water potential of -150 kPa to a solution with -50 kPa over 10 minutes. Use the formula: Water flux (L/min) = (change in water potential difference) / (time in minutes).

Answer: Water flux = (|-50 - (-150)|) / 10 = 100 / 10 = 10 litres per minute.

Question 5: Identify three variables that could affect the rate of osmosis in an experiment involving potato slices submerged in different solutions.

Answer: Concentration of solution, temperature, size and surface area of potato slices.

Question 6: What safety precautions should be taken when handling solutions in osmosis experiments involving chemicals like sodium chloride or sucrose?

Answer: Wear safety goggles, gloves, and handle chemicals carefully to avoid skin contact or ingestion. Work in a well-ventilated area.

Question 7: Explain why a cell placed in pure water will swell and potentially burst.

Answer: In pure water, the water potential outside the cell is higher than inside, so water moves into the cell by osmosis. This influx of water causes the cell to swell and may lead to bursting if the cell membrane cannot withstand the pressure.

Question 8: Describe a practical experiment to demonstrate osmosis using potato slices. Include the variables you would control and measure.

Answer: Cut uniform potato slices and submerge them in solutions of varying salt concentrations. Control variables include slice size, temperature, and duration. Measure the change in weight of each slice before and after immersion to assess water movement. Higher salt concentrations will cause more water to exit the potato cells.

Question 9: In a food industry setting, how is osmosis utilised in the process of dehydration of fruits?

Answer: Osmosis is used to draw water out of the fruit by immersing it in a hypertonic solution, reducing moisture content and preventing microbial growth during preservation.

Question 10: Explain how understanding osmosis can help in treating medical conditions related to fluid imbalance.

Answer: Knowledge of osmosis helps in managing conditions like oedema or dehydration by controlling fluid intake and using solutions with specific water potentials in IV therapy to restore proper fluid balance across cell membranes.