5.5 Osmosis

Question 1

Water potential

Answer 1

Pressure exerted by water molecules as they collide with a membrane/container

Question 2

Units and symbol for water potential

Answer 2

Pascals or Kilopascals

Symbol - psi ψ

Question 3

Water potential of pure water

Answer 3

0 kPa

Highest possible value

Question 4

Water potential of solutions

Answer 4

Negative water potentials

More concentrated - more negative water potential

Question 5

Osmosis

Answer 5

Net movement of water from an area of high water potential to an area of low water potential across a partially permeable membrane

Question 6

What happens when an animal cell is placed in solution with higher water potential?

Answer 6

Water moves in by osmosis

Cell swells and bursts

Question 7

What happens when an animal cell is placed in solution with lower water potential?

Answer 7

Water leaves the cell by osmosis

Cell shrinks, crenation occurs

Question 8

Cytolysis

Answer 8

Bursting of a cell

Question 9

What happens when a plant cell is placed in solution with higher water potential?

Answer 9

Water enters the cell by osmosis
Increased hydrostatic pressure pushes membrane against the rigid cell walls
Turgor pressure increases - cell becomes turgid
Cellulose cell wall prevents cytolysis

Question 10

What happens when a plant cell is placed in solution with lower water potential?

Answer 10

Water is lost by osmosis
Cytoplasm pulls away from the cell surface membrane
Cell is plasmolysed