2.5.3- Osmosis

Question 1

Define what water potential is.

Answer 1

The measure of the tendency of water molecules to diffuse from one region to another

Question 2

Define what a solvent is.

Answer 2

The liquid in which dilute molecules are dissolved in.

Question 3

In what type of solution would water be the solvent?

Answer 3

An aqueous solution.

Question 4

Explain the effect adding solute molecules to water has on the relative number of water molecules in the solution.

Answer 4

The relative number of water molecules is reduced.

Even further if the solvent dissociates to ions, as there are more particles of the solvent in the solution

Question 5

Pure water has the _______ possible water potential.

Answer 5

Highest

Question 6

Explain the effect the addition of solute molecules will have on the water potential of the solution

Answer 6

The solute molecules will LOWER the water potential.

Question 7

When two aqueous solutions of different water potentials are separated by a partially permeable membrane, what will happen?

Answer 7

The water molecules will diffuse via osmosis from the solution with the highest water potential to the lowest water potential.

Question 8

Explain what happens when the water potential on either side of the partially permeable membrane reaches equilibrium.

Answer 8

There will be no net osmosis, but the water molecules continue to move randomly.

Question 9

What is water potential measured in?

Answer 9

Kilopascals (kPa).

Question 10

Pure water has the highest water potential and is given what value?

Answer 10

A water potential value of 0kPa- 0 kilopascals.

Question 11

Explain what galleons to the kilopascal value of water potential as more solute molecules are added to the solution.

Answer 11

As more solute molecules are added, the kPa value gets more negative.

Question 12

Explain the difference and reasoning behind the water potential of pure water and the water potential in cytoplasm and the large vacuole of plant cells.

Answer 12

The water potential is lower in the vacuole and cytoplasm as there are solutes present in them.

Question 13

Explain what Will happen when cells are placed in a solution of higher water potential than that of inside the cell.

Answer 13

The water molecules will move into the cell via osmosis and down the concentration gradient

Question 14

Explain what will happen to an animal cell if too much water moves into the cell via osmosis.

Answer 14

The cell will swell and burst as the plasma membrane will break- this is called cytolysis.

Question 15

Explain what will happen to plant cells if a large amount of water molecules moves into the cell via osmosis.

Answer 15

The rigid cellulose cell wall will prevent bursting and the cell will swell to a point where it pushes against the wall to resist further swelling- the swollen cell is TURGID.

Question 16

When cells are left in a solution with a lower water potential than the contents of the cell, explain what will happen.

Answer 16

Water will move out of the cell as it moves from an area of higher water potential to lower water potential via osmosis.

Question 17

What happens to ANIMAL cells when they are placed in solution of lower water potential than the cell.

Answer 17

The animal cell shrivels up and is described as CRENATED.

Question 18

Explain what will happen to a PLANT cell when placed in a solution of lower water potential than its contents.

Answer 18

Water moved out of the cell, causing the cytoplasm to shrink and the membrane to pull away from the cell wall. The cell is PLASMOLYSED. plant tissue with Plasmolysed calls is described as FLACCID.

Question 19

Explain the effects that plasmolysed cells can have on themselves.

Answer 19

They can suffer a degree of dehydration and their metabolism cannot proceed as the enzyme catalysed ready ions need to be in solution to work.

Question 20

Define what osmosis is.

Answer 20

The passage of water molecules across a partially permeable membrane and down their water potential gradient.