Core component 3- Determination Of Water And Solute Potentials Flashcards Preview

Eduqas A level Biology - Year 1 > Core component 3- Determination Of Water And Solute Potentials > Flashcards

Flashcards in Core component 3- Determination Of Water And Solute Potentials Deck (14)
Loading flashcards...
1
Q

What is the water potential of pure water?

A

0Kpa

2
Q

What happens when you add a solute to pure water?

A

It lowers the water potential and brings water molecules in - this pull in gives a negative water potential

3
Q

How does more solute effect solute potential?

A

The more solute present, the more tightly water molecules are held, the lower the tendency of water to move out. So a higher concentration has a more negative solute potential .

4
Q

What happens to the pressure potential when water enters a plant cell?

A

The vacuole and cytoplasm expand and are pushed up against the cell wall. The cell wall cannot expand and therefore pressure outwards builds up, resisting entry of more water, making the cell turgid. Larger the push outwards, larger the pressure potential.

5
Q

What is the water potential equation?

A

Water potential = pressure potential + solute potential

6
Q

What is a hypotonic solution?

A

The external solution is less negative than the solution inside the cell, so water flows into the cell

7
Q

What is a hypertonic solution?

A

Water potential of the external solution is more negative than the solution inside the cell - so water flows out of the cell

8
Q

What is an isotonic solution?

A

The cells has the same water potential as the surrounding solution so there will be no net movement of water

9
Q

In terms of the water potential equation what happens when a cell is fully turgid?

A

Water potential = 0
Pressure potential = -solute potential

As water enters cells, the contents pushes more on the cell wall increasing the pressure potential. The pressure rises until it’s equal opposite of the solute potential. At that point no more water can enter and as there is no tendency for the cell to absorb water, it’s water potential is 0.

10
Q

In terms of the water potential equation what happens at incipient plasmolysis?

A

Pressure potential = 0kpa
Water potential = solute potential of external solution

At incipient plasmolysis the cell has lost just enough water to pull away from the cell wall and therefore the cell wall does not exert any pressure on the cytoplasm.

11
Q

In terms of the water potential equation what happens when a cell is fully plasmolysed?

A

Pressure potential = 0
Water potential > solute potential of external solution

When the cell loses water this causes the vacuole and cytoplasm to shrink and move away from the cell wall - the cell cannot support itself and therefore becomes flaccid, if it loses too much water the plant can wilt and die.

12
Q

How do you work out water potential in animal cells?

A

Animal cells have no cell wall so pressure potential does not have to be considered, therefore water potential = solute potential

13
Q

What happens if red blood cells are placed in distilled water?

A

Water enters by osmosis and goes down a water potential gradient. The red blood cells continue to expand and due to them having no cell wall to resist the expansion they will burst - haemolysis.

14
Q

What happens if red blood cells are placed in concentrated salt solution?

A

Water moves out by osmosis, from an area of higher water potential to an area of lower water potential. This causes the red blood cell to shrink and become crenated.

Decks in Eduqas A level Biology - Year 1 Class (53):