Osmosis in plants

Question 1

What are the 5 features of a simple plant cell which are elevant in terms of osmosis….

Answer 1

1. Cell wall
2. Cell surface membrane
3. Cytoplasm
4. Tonoplast
5. Vacuole

Question 2

What is the concentration of disolved substances inside the cell called

Answer 2

Solute potential

Question 3

What is the solute potential 𝟁_s

Answer 3

A measure of the reduction in water potential due to the presence of solute molecules

Question 4

What is the potential of pure water

Answer 4

Zero

Question 5

What happens when you lower the potential of water

Answer 5

The movement of water molecules is reduced

The solute potential is therefore always negative

Question 6

Is the solute potential positive or negative

Answer 6

Always negative

Because it reduces the potential of water

Question 7

When there are large nos of solute molecules present is the water is ths potential high or low

Answer 7

Low

Question 8

When there are small nos of solute molecules present is the water potential high or low

Answer 8

High

Question 9

Why does water pass into a vacuole

Answer 9

The vacuole has a lot of solute molecules, a low solute potential

Water molecules pass into the vacuole because it has a lower internal solute potential than the external water potential

Question 10

What is the pressure potential 𝟁_p

Answer 10

The pressure exerted on the cell contents by the cell wall and cell membrane.

It is usually positive but not always.

Question 11

When does water enter the cell

Answer 11

When the solute potential inside the cell is lower than the water potential outside the cell

Question 12

What happens when water enters the cell

Answer 12

The cell contents starts to swell, and the cellulose cell membrane starts to stretch

It does not go on forever however, as the cell membrane stretches to its capacity, it starts to resist the inflow of water molecules

The pressure which develop in the cell wall is the pressure potential

It is usually but not always positive

Question 13

What is the calculation for the water potential of a cell 𝟁

Answer 13

Water potential 𝟁 = solute potential 𝟁_s + pressure potential 𝟁_p

Question 14

What is the name given to a week solution

Answer 14

Hypotonic

HYPO TONIC

Question 15

When is a plant cell said to be turgid

Answer 15

• When the water potential inside the cell is lower than the water potential outside of the cell
• Water enters the cell via osmosis and it expands
• Once the water potential within the cell is the same as the water potential on the outside of the cell it is said to be TURGID

Question 16

What are the features of turgid cells

Answer 16

• Firm
• Full of water
• Plants are upright

Question 17

What is plasmolysis

Answer 17

When the water potential outside the cell is lower than the water potential inside the the cell

The cell starts to push water out of the cell

When the water potential inside the cell is equal to the water potential outside of the cell

The cell is described as flacid

In this situation the stem cell starts to wilt.

Question 18

What would happen if you fed an isotonic solution

Answer 18

Nothing

The water potential outside of the cell would be the same as the isotonic solutions

Isotonic means the same…