Osmosis

Question 1

What is osmosis?

Answer 1

Osmosis is the diffusion of water molecules across a partially permeable membrane from an area of high water potential to an area of low water potential

Question 2

What is a ‘solution’?

Answer 2

Mixtures made up of a solute dissolved in a solvent

Question 3

What is a ‘solute’?

Answer 3

Something that is dissolved in a solvent

Question 4

What is a ‘solvent’?

Answer 4

Liquid that a solvent dissolves in

Question 5

What is meant by ‘water potential’?

Answer 5

The pressure that is exerted by water molecules on the membrane surrounding a solution

Question 6

What is water potential measured in?

Answer 6

KiloPascals (kPa)

Question 7

What is meant by ‘high water potential’ in a solution?

Answer 7

The solution has a high water concentration so not much solvent dissolved in it

Question 8

What is meant by ‘low water potential’ in a solution?

Answer 8

The solution has a low water concentration so has lots of solvent dissolved in it

Question 9

What are the 3 types of solutions?

Answer 9

1) Hypotonic
2) Isotonic
3) Hypertonic

Question 10

What is a hypotonic solution?

Answer 10

A solution that has a higher water potential than the cell

Question 11

If a cell was placed in a hypotonic solution, what would happen?

Answer 11

Water molecules would move into the cell and it will swell and burst
- However plant cells don’t burst due to their cell wall

Question 12

What is an isotonic solution?

Answer 12

A solution that has the same water potential as the cell

Question 13

If a cell was placed in an isotonic solution, what would happen?

Answer 13

No net movement of water in or out of the cell and the cell remains the same size

Question 14

What is a hypertonic solution?

Answer 14

A solution that has a lower water potential than the cell

Question 15

If a cell was placed in a hypertonic solution, what would happen?

Answer 15

Water molecules move out of the cell and the cell will shrink and if the cell is a plant cell, it will also become plasmolysed

Question 16

What are the 4 key factors that affect the rate of osmosis?

Answer 16

1) Temperature
2) Water potential gradient
3) Thickness of membrane
4) Surface area

Question 17

How does higher temperatures affect the rate of osmosis?

Answer 17

At higher temperatures, water molecules have more kinetic energy and will diffuse faster

Question 18

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

Answer 18

The steeper the gradient, the faster rate of osmosis

Question 19

How does the thickness of the membrane affect the rate of osmosis?

Answer 19

If a cell membrane is thin, water molecules will travel shorter distances and will diffuse faster

Question 20

How does surface area affect the rate of osmosis?

Answer 20

Larger surface area allows for more water molecules to cross the membrane at once, which speeds up the rate of osmosis