5.5 Osmosis

Question 1

What is a solute

Answer 1

Substance dissolved in a solvent forming a solution

Question 2

What is water potential

And what’s it’s measured in

Answer 2

Pressure exerted by water molecules as they collide with a membrane or container
Units of pressure pascals (Pa) or kilopascals (kPa)

Question 3

What is the water potential of pure water

Answer 3

0 kPa

Highest possible value for water potential

Question 4

Why is 0kpa the highest possible value for water potential

Answer 4

Presence of a solute in water lowers the water potential below 0
So all solutions have negative water potentials

Question 5

When does osmosis happens

Answer 5

When solutions of different concentrations are separated by a partially permeable membrane
A net movement of water with the higher water potential ( less concentrated) moves to the solution with lower water potential

Question 6

What is the increase in pressure called when water enters cells

Answer 6

Hydrostatic pressure

Same units as water potential kPa

Question 7

What happens if an animal cell is placed in a solution with a higher water potential than that of its cytoplasm

Answer 7

Animal cell is less concentrated so water will move into the cell increasing its hydrostatic pressure

Question 8

What is cytolysis

Answer 8

Increase of hydrostatic pressure that the cell membrane cannot with old so it breaks and burst

Question 9

What happens if an animal cell if it’s placed in a solution with a lower water potential that it’s cutoplams

Answer 9

Animal cell is more concentrated so It will lose water to the solution.
Causing a reduction in volume and causing the cell distance membrane to pucker
Crenation

Question 10

What can’t plants cells do that animal cells can with water

Answer 10

Can not control the water potential of the fluid around them

Question 11

What happens to plants cells when water enters them

Answer 11

Increase in hydrostatic pressure
This pushes the membrane against the rigid cell walls causing turgor

As turgor pressure increases the resists the entry of further water and the cell becomes turgid

Question 12

What is pressure against cell wall in plant cells called

Answer 12

Turgor

Question 13

What happens to plant cells when water is lost from its cells

Answer 13

Reduction in volume of cytoplasm eventually pulling the cell surface membrane away from the cell wall
Cell is plasmolysed