Diffusion and Osmosis

Question 1

What is the cell membrane described as in terms of permeability?

Answer 1

It is a semi permeable membrane- so it allows some molecules through but not all

Question 2

What does the cell membrane do?

Answer 2

It is selectively permeable so controls what substances enter and leave the cell

Question 3

What processes are in cell membrane that aid transport?

Answer 3

• diffusion
  -osmosis
  -active transport

Question 4

Define diffusion:

Answer 4

Diffusion is the movement of molecules from an area of high concentration to an area of low concentration

Question 5

What are passive processes ?

Answer 5

Passive processes require no energy
eg diffusion and osmosis

Question 6

Examples of diffusion

Answer 6

• co2 diffusion into a leaf
• oxygen diffusing from the blood into the cell
• smell of perfume
• food colouring in water

Question 7

What are the factors affecting diffusion?

Answer 7

-Temperature
-Concentration
-Particle size

Question 8

Hoe does temperature affect diffusion?

Answer 8

The higher the temperature the more kinetic energy the molecules have so the faster the rate of diffusion

Question 9

Hoe does concentration affect diffusion?

Answer 9

The higher the concentration of particles the greater the difference in concentration gradient and the greater the rate of diffusion

Question 10

Define osmosis

Answer 10

Osmosis is the diffusion of water molecules from an area of high water molecules concentration to an area of low water molecule concentration

Question 11

Hoe does particle size affect diffusion?

Answer 11

The smaller the particle size the faster the rate of diffusion

Stirring speeds up diffusion

Question 12

What is a solvent?

Answer 12

A solvent is a liquid that dissolves other substances

Question 13

What is a solution?

Answer 13

A solution is a mixture of solvent and solute

Question 14

What is a solute?

Answer 14

Is a substance that has been dissolved in a solvent

Question 15

What is a concentrated solution?

Answer 15

It is a solution with a large amount of solute in comparison with solvent

Question 16

What is a dilute solution?

Answer 16

It is a solution with a large amount of solvent in relation to solute

Question 17

What is a hypertonic solution?

Answer 17

A hypertonic solution is one that contains a large amount of solute in relation to solvent eg concentrated

cells shrivel

Question 18

What is a hypotonic solution?

Answer 18

A hypotonic solution is one that contains a large amount of solvent in relation to solute eg dilute

cells swell or burst

Question 19

What is a isotonic solution?

Answer 19

An isotonic solution is one that contains the same ratio of solvent and solution

osmosis does not occur

Question 20

What happens to animal cells in a solution that is the same concentration as the cytoplasm?

Answer 20

In a solution that is of the same concentration than that of the cytoplasm
- there is no net movement as water moves in and out of the cell at the same rate
-there is no change in volume

Question 21

What happens to animal cells in a solution that is less concentrated than the concentration of the cytoplasm?

Answer 21

Water from the outside of cell will move into the cell as the outside will have a higher concentration of water molecules

Question 22

What happens to animal cells in a solution that is more concentration than the concentration of the cytoplasm?

Answer 22

If a cell is surrounded by a more concentrated solution it means there are less water molecules outside the cell than inside the cytoplasm so
- water will move out of the cell and it will shrivel

Question 23

Are cell walls fully permeable or semi permeable?

Answer 23

cell walls = fully permeable

Question 24

What happens to a plant cell in a less concentrated solution than that of the inside of the cell?

Answer 24

There will be a higher concentration of water molecules outside the cell so
-water will move into the cytoplasm and vacuole
- causes cell to slightly swell and the vacuole to push the cytoplasm up against the cell wall

Question 25

Define turgor pressure?

Answer 25

It is the outward pressure exerted by the vacuole and cytoplasm against the cell walls

Question 26

What does the turgor pressure do to the plant cell?

Answer 26

The cell wall is rigid so prevents the cell bursting Without the turgor pressure plants would wilt Turgot pressure gives the plant cell great strength

Question 27

What happens to a plant cell in a more concentrated solution than that of the inside of the cell?

Answer 27

There will be less water molecules outside the cell than insoide the cell so water will move out of the cell It causes the vacuole and cell membrane to shrivel Cell wall is not as strong cell becomes flaccid

Question 28

What is it called when a cell become flaccid?

Answer 28

A cell is said to be plasmolysed as plasmolysis has occurred Water has left the plant cell and vacuole and cell membrane have shrivelled

Question 29

How does osmosis aid food preservation?

Answer 29

Osmosis can be used to kill bacteria and fungi in order to prevent them from growing on food

Question 30

Why is fish and meat placed in salty water?

Answer 30

Bacteria and Fungi have cell walls -If the bacteria and fungi are placed in this salty water they will loose water by osmosis and die

Question 31

Why are fruits placed in water of a high sugar concentration?

Answer 31

If the bacteria and fungi are placed in a high sugar concentration there will be a higher water concentration inside the bacteria and fungi cells than outside so - water will leave these cells and they will die

Question 32

What experiment can be done to demonstrate osmosis?

Answer 32

Visking tubing containing different concentrated solutions in a beaker of water

Question 33

How do you detect change?

Answer 33

Measure the mass and turgidity of each visking tube before and after placing in the water beaker for 30 minutes

Question 34

What do you fill the two bags with?

Answer 34

one- distilled water two- sucrose solution

Question 35

What will happen to the visking tube filled of sucrose solution after 30 mins?

Answer 35

The tube will fill with water as the water move in from an area of high water to conc to an area of lower conc which is inside the tubing. So the mass increases and the turgidity increases too

Question 36

What will happen to the visking tube filled with distilled water after 30 mins?

Answer 36

There will be no change in the mass or turgidity of the visking tube as the conc on each side of the visking tube are equal s there is no concentration gradient results in no net movement