Required Practical 3 Flashcards
(25 cards)
What should cells or tissues have the water potential in an experiment?
The same (sugar content)
What should cells and tissues be genetically?
There should be no genetic differences between the cells/tissues.
Is potato skin permeable to water?
The potato skin is impermeable to water.
How is potato skin different from other tissues in terms of water movement?
Potato skin is a different tissue from the rest of the potato.
Why does the skin have different water potential compared to the rest of the potato?
The cells of the skin have different water potential than the rest of the potato.
Why should the surface area of the tissue be the same in an experiment?
The surface area should be the same to ensure consistent results.
How does surface area affect water uptake?
Differences in surface area would affect the rate of water uptake or loss.
How do you calculate the change in mass for the experiment?
Find the change in mass (final mass - initial mass).
How do you calculate the rate of water uptake or loss over time?
Divide the change in mass by the time (e.g., 30 minutes).
Why does mass increase in low molarity sucrose solutions (0-0.3 mol/dm³)?
The water potential outside is higher (less negative) than inside, so water enters the cells by osmosis.
Why does the mass stay the same at 0.3 mol/dm³ sucrose solution?
The sucrose solution has the same water potential as the inside of the cells, so there’s no net movement of water.
Why does mass decrease in higher molarity sucrose solutions (0.3-0.8 mol/dm³)?
The water potential outside is lower (more negative), so water leaves the cells by osmosis.
Why is there no further mass loss at higher sucrose concentrations?
There is no further loss of water because all cell water has moved out, causing the cells to plasmolyze.
What is a method to prepare a dilution series?
Use a serial dilution method to prepare the series.
What should be done to the axes of the graph?
The axes should be correctly labelled, with mol/dm³ and ratio (without units).
How should data points be plotted on the graph?
The correct values should be plotted accurately, and a smooth curve should be drawn.
Why does water move out of the potato cells in a sucrose solution?
The sucrose solution has a more negative water potential than the potato cytoplasm.
How does water move across the potato cell membrane in a hypertonic solution?
Water moves out of the potato cells into the sucrose solution by osmosis.
What happens to the mass of the potato cells in a hypertonic sucrose solution?
The cells decrease in mass due to water loss.
How can you ensure all cut surfaces of the potato cubes are exposed to the solution?
Ensure that all cut surfaces of the potato cubes are fully submerged in the sucrose solution.
What is one method to control temperature during the experiment?
Conduct the experiment at room temperature to keep conditions consistent.
Why should the potato cubes be dried before measuring?
Dry the cubes to prevent water from being weighed that was outside the cells.
How often should you measure the mass of the potato cubes?
Measure the mass of the cubes at regular time intervals (e.g., every 5 minutes for up to 40 minutes).
How do you calculate the rate of osmosis per unit area for each set of data?
Calculate the rate of osmosis by dividing the change in mass by the surface area of the cubes.
