Diffusion and Osmosis (Complete)

Question 1

What is a membrane?

Answer 1

A lipid bilayer with embedded protein.

Question 2

Where are biological membranes found?

Answer 2

Cell membranes.
Membranes surrounding:
Nucleus
Chloroplasts
Mitochondria

Question 3

What is a selectively permeable membrane?

Answer 3

A selectively permeable membrane only allows some substances through.

Question 4

What substances do selectively permeable membranes allow through?

Answer 4

Water
Carbon dioxide
Oxygen

Question 5

What substances do selectively permeable membranes not allow through?

Answer 5

Larger sugars
Salts
Proteins

Question 6

Where are selectively permeable membranes located?

Answer 6

Chloroplasts
Surrounding the nucleus
Vacuoles
Mitochondria

Question 7

What is a permeable membrane?

Answer 7

A permeable membrane allows all substances through.

Question 8

Give an example of a permeable membrane.

Answer 8

Cell wall

Question 9

What is diffusion?

Answer 9

Diffusion is the passive movement of substances from a region of higher concentration to a region of lower concentration through a concentration gradient. Does not require ATP energy.

Question 10

What is another name for diffusion, why?

Answer 10

Passive transport, as it does not require ATP energy.

Question 11

Describe diffusion in the lungs.

Answer 11

Oxygen diffuses into the blood

Carbon dioxide difuses from the plasma into the alveoli

Question 12

Describe diffusion in the leaf.

Answer 12

Oxygen diffuses out through the stomata into the atmosphere

Carbon dioxide diffuses into mesophyll cells in the leaf

Question 13

Describe diffusion in the blood.

Answer 13

Oxygen diffuses from the blood into tissue cells

Carbon dioxide diffuses from the tissue cells into the blood

Question 14

Name three factors that affect diffusion

Answer 14

Temperature
Concentration
Distance

Question 15

How does temperature affect the rate of diffusion?

Answer 15

The higher the temperature, the faster the rate of diffusion

Question 16

How does concentration affect the rate of diffusion?

Answer 16

The greater the concentration difference between the two regions, the faster the rate of diffusion

Question 17

How does distance affect the rate of diffusion?

Answer 17

The shorter the distance between the two regions, the faster the rate of diffusion
That is why:
Leaves are thin
Alveoli wall is one cell thick

Question 18

What is active transport?

Answer 18

The movement of substances from a region of lower concentration to a region of higher concentration along a concentration gradient. Requires ATP energy

Question 19

What is osmosis?

Answer 19

The movement of water molecules along a selectively permeable membrane from a region of high water concentration to a region of low water concentration

Question 20

Why is osmosis considered a special type of diffusion?

Answer 20

Because osmosis is the diffusion of water along a selectively permeable membrane

Question 21

How does a plant cell become turgid?

Answer 21

Plant cell contains more concentrated solution than its surroundings
Water enters the sap vacuole and cytoplasm by osmosis
Cell swells up against the restraining cell wall
Exerts outward turgor pressure- turgor is defined as the pressure of the cell contents up against the inelastic cell wall
Plant cell does not burst as cell wall is not very elastic
Plant cell is now turgid- the rigid expanded state of a plant due to the entry of water by osmosis

Question 22

How does a plant cell become plasmolysed?

Answer 22

Plant contains less concentrated solution than its surroundings.
Water exits the cytoplasm and sap vacuole by osmosis.
Cell shrinks and the cell membrane pulls away from the cell wall.
As the cell wall is fully permeable, external solution fills up the empty space.
The inelastic cell wall prevents the cell from bursting.
The cell is now plasmolysed. Plasmolysed means the loss of turgour due to water leaving the plant cell by osmosis causing the cell membrane to pull away from the cell wall.

Question 23

Explain the biological basis of using high sugar or high salt concentration in the preservation of food.

Answer 23

Bacteria and fungi lose water by osmosis, and become inactive allowing food to be preserved.

Question 24

What is turgor?

Answer 24

Turgor is the pressure of cell contents up against the restraining cell wall.

Question 25

What happens to a plant if it loses turgidity?

Answer 25

It wilts

Question 26

What would happen if an animal cell were to become turgid?

Answer 26

It would burst as theres no inelastic cell wall.