3.2.3.3 Osmosis

Question 1

The passive movement of water from an area of high water potential to an area of low water potential through a selectively permeable membrane is…

Answer 1

Osmosis

Question 2

Osmosis involves the movement of

Answer 2

Water ONLY

Question 3

By adding more solute than a solution, how does this affect the water potential

Answer 3

It lowers the water potential - becomes more negative

Question 4

Why does pure water have a higher water potential than a solution of sugar

Answer 4

There are more “free” water particles in pure water

Question 5

A potato has a WP of -200kPa was placed in pure water WP of 0kPa, what happens?

Answer 5

Water ENTERS the potato by osmosis (water moved from a high water potential to a lower water potential)

Question 6

Water potential is measured in units of pressure which are..

Answer 6

kPa

Question 7

Pure water has a water potential of

Answer 7

0kPa

Question 8

How can you determine the water potential of a potato

Answer 8

Place potato in a series of solutions of different WP. Where there is no net gain of water by the potato is the WP of the potato

Question 9

What happens if a red blood cell is placed in pure water?

Answer 9

It swells and bursts - water enters the cell

Question 10

What happens if a red blood cell is placed in strong sugar solution

Answer 10

It shrinks - water leaves the cell

Question 11

What hapens if a plant cell is placed in pure water

Answer 11

It swells - water enters the cell - it becomes turgid

Question 12

What happens if a plant cell is placed in strong salt solution

Answer 12

Water leaves the cell - it shrinks - it is plasmolysed

Question 13

What is meant by selectively permeable

Answer 13

Membrane only allows certain molecules through, it is only permeable to water and other small molecules

Question 14

During an osmosis practical, how and why do you dry the potatos

Answer 14

With a paper towel

To remove surface water - this would add to the mass which we do not want

Question 15

You must control the temperature during your osmosis practical - HOW?

Answer 15

Using a water bath and check the temperature at regular intervals using a thermometer

Question 16

Give 2 similarities in the movement of substances by diffusion and osmosis

Answer 16

1. Down a gradient (high to low)

2. Passive not active (does not use energy)