osmosis Flashcards
What is Osmosis?
The net movement of water from an area of high water potential to an area of low water potential, through a partially permeable membrane.
Compare and contrast how water and ions enter cells.
Comparison: both move down concentration gradient; Comparison: both move through protein channels in membrane; Contrast: ions can move against a concentration gradient by active transport
Give two similarities between diffusion and osmosis
Movement is down a concentration gradient; Both are passive processes;
What is the highest water potential? And what happens when you add a solute?
Pure water has a water potential of 0. When any solute is added the solution becomes more negative.
When investigating osmosis, why do you need to blot the potato before weighing it?
Water will affect the mass, and we only want to measure water taken up or lost; Amount of water on cylinders varies so it ensures same amount of water on outside;
How do you calculate the volume of stock solution needed?
Concentration needed x volume needed
Concentration of stock solution
Why do we calculate the percentage change/a ratio of initial to final mass?
Allows comparison or shows proportional change; As the cylinders have different starting masses;
Why does repeating the experiment improve reliability?
A mean can be calculated; the effect of anomalies can be minimised by identifying them and discarding;
Describe how you would use the student’s results in the table above to find the water potential of the potato tissue.
Plot a graph with concentration on the x-axis and percentage change in mass on the y-axis; Find the concentration where percentage change is zero; Use a table to find water potential of solute concentration where curve crosses x-axis.
Explain why a chipped potato would loss mass in a salty solution
Water potential of solution is more negative than that of potato tissue; Tissue loses water by osmosis;
