4.3 Osmosis

Question 1

What is osmosis?

Answer 1

The passage of water from a region where it has a higher water potential to one where it has a lower water potential through a selectively permeable membrane.

Question 2

what is water potential?

Answer 2

The pressure created by water molecules.

• measured in KPa
• represented by the greek letter psi
• at standard temperature and pressure water potential has a water potential of 0

Question 3

What effects water potential?

Answer 3

• the addition of a solute will lower water potential
• a solution always has a negative value
• during osmosis a solution moves from a region of higher (-20) WP to a region of lower (-30) WP

Question 4

What happens if you place an animal cell in solutions of varying water potential?

Answer 4

• if the solution has a higher water potential, the cell will take in the water. if it takes in too much then the cell membrane will burst
• if the solution has the same water potential, no water will be taken in or leave the cell
• if the solution has a lower water potential then water will leave and the cell will become shrivelled.