Cell Membranes- Osmosis

Question 1

What is osmosis?

Answer 1

The diffusion of water molecules across a selectively permeable membrane from an area of higher water potential to an area of lower water potential

Question 2

What is water potential?

Answer 2

The pressure created by water molecules

Question 3

What has the highest water potential?

Answer 3

Pure water

Question 4

What are two solutions called if they have the same water potential?

Answer 4

Isotonic

Question 5

What are the three factors that the rate of osmosis depends on?

Answer 5

Water potential gradient, thickness of exchange surface, surface area

Question 6

How does the water potential gradient affect the rate of osmosis?

Answer 6

Higher water potential gradient, faster rate of osmosis

Question 7

How does the thickness of the exchange surface affect the rate of osmosis?

Answer 7

Thinner the exchange surface, faster rate of diffusion

Question 8

How does the surface area affect the rate of osmosis?

Answer 8

Larger surface area, faster rate of osmosis

Question 9

How do you investigate water potential?

Answer 9

Using potato cylinders by using serial dilutions

Question 10

How do you make serial dilutions?

Answer 10

1. Line up 5 test tubes in a rack
2. Add 10cm3 of 2M sucrose solution to first test tube and 5cm3 of distilled water to other 4 test tubes
3. Draw 5cm3 of solution from first test tube using a pipette and add to distilled water in second test tube and mix solution
4. Repeat process 3 more times

Question 11

How do you use solutions to find water potential of potato cells?

Answer 11

1. Use cork borer to cut identical potato chips
2. Measure mass of chips
3. Place one chip in each solution
4. Leave chips in each solution for around 20 minutes
5. Weigh chips again and record results
6. Calculate % change in mass
7. Use results to make a calibration curve