Cells - Transport across cell membrane - 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 the a solution how does this affect the water potential

Answer 3

it lowers the WP - 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 0kPa, what happens?

Answer 5

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

Question 6

water potential is represented by

Answer 6

psi (greek letter)

Question 7

water potential is measured in units of pressure which are

Answer 7

kPa

Question 8

Pure water has a WP of

Answer 8

0kPa

Question 9

How can you determine the the WP of a potato

Answer 9

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 10

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

Answer 10

it swells and bursts - water enters the cell

Question 11

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

Answer 11

It shrinks - water leaves the cell

Question 12

What happens if a plant cell is placed in pure water

Answer 12

It swells - water enters the cell - it becomes turgid

Question 13

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

Answer 13

water leaves the cell - it shrinks - it plasmolysed

Question 14

What is meant by selectively permeable

Answer 14

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

Question 15

During an osmosis practical, how and why do you dry the potato chips?

Answer 15

with a paper towel. To remove surface water - This would add to the mass - which we do not want

Question 16

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

Answer 16

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

Question 17

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

Answer 17

1. down a gradient (High to Low)

2. passive not active (does not use energy)