Diffusion And Osmosis

Question 1

Permeable vs impermeable

Answer 1

Substances can pass through
Substances cannot pass through

Question 2

Selectively permeable

Answer 2

Allows some substances to pass through, but blocks others

Question 3

Selectively permeable in cells

Answer 3

Allow water, CO2, O2 to pass through freely, but not sugars, salts and proteins to pass through easily.

Have specialised mechanisms to allow substances to pass through eg. Glucose for respiration

Question 4

Biological membranes examples

Answer 4

Cell
Mitochondria
Chloroplasts
Nucleus

Question 5

Diffusion

Answer 5

The spreading out of molecules from a region of high concentration to a region of low concentration

Question 6

Active transport

Answer 6

The movement of molecules from a less concentrated to a more concentrated area with the use of energy.

Question 7

Movement through membranes

Answer 7

Diffusion and active transport

Question 8

Diffusion in everyday life

Answer 8

Smell of perfume
Bread baking
Stink bomb
Food colouring in water
Teabag in hot water

Question 9

Diffusion in biology

Answer 9

CO2 and O2 diffusing in and out of leaf

CO2 and O2 diffusing in and out of body cells

Question 10

Osmosis

Answer 10

The movement of water molecules across a semi-permeable membrane , from a region of high water concentration to a region of low water concentration

• special type of diffusion that does not require energy
• form of passive transport

Question 11

Solvent

Answer 11

A liquid that dissolves another substance

Question 12

Solute

Answer 12

A substance that has been dissolved

Question 13

Solution

Answer 13

Mixture of a solute and a solvent

Question 14

What happens if pure water is separated from salt water

Answer 14

• water molecules move randomly on both directions
• salt molecules cannot move out so more water moves into the salt solution

Question 15

Give the three states of osmosis and animal cells

Answer 15

Isotonic, hypertonic, hypotonic

Question 16

What do animals in the sea have

Answer 16

A cytoplasm with the same salt concentration as sea water

Question 17

What do land animals have that ensures the blood concentration is the same as the cells cytoplasm

Answer 17

Kidneys

Question 18

Isotonic medium

Answer 18

If an animal cells is in a solution that is the same concentration as its cytoplasm, water will move in and out at the same rate and the cell remains intact

Question 19

Hypotonic medium

Answer 19

If an animal cell is in a solution that is less concentrated than its cytoplasm, water will move into the cell

• the cell may burst and die

Question 20

Amoeba

Answer 20

Single celled organisms that live in freshwater ponds
- have a contractile vacuole

Question 21

Contractile vacuole

Answer 21

Expels water, to prevent amoeba from bursting

Animals that live in sea water do not have a contractile vacuole

Question 22

State the steps of contractile vacuole

Answer 22

1. Water enters amoeba by osmosis
2. Excess water enters contractile vacuole
3. Contractile vacuole swells
4. Contractile vacuole moves to edge of cell
5. Contractile vacuole bursts and expels water
6. Cycle is repeated

Question 23

Hypertonic medium

Answer 23

If an animal cell is in a solution that is more concentrated than its cytoplasm, water will move out of the cell

• the cell will shrivel and possibly die

Question 24

Cell walls

Answer 24

Plant cells have a membrane surrounded by a cell wall
- cells walls are fully permeable to water, gases and many solutes

Question 25

How do roots absorb water from the soil

Answer 25

If a plant cell has a higher concentration of solutes than its surroundings, water moves into the cytoplasm and vacuole.

Question 26

Turgor pressure

Answer 26

Water enters the vacuole of the plant cell, and pushes the cytoplasm against the cell wall

Question 27

Role of turgor pressure

Answer 27

-Cell wall is rigid and prevents the cell from swelling

• turgor pressure gives plant cells strength
  (Plants that do not have wood get strength from their cells being fully turgid)

Question 28

3 states of plant cells and osmosis

Answer 28

Turgid (hypotonic solution)
Flaccid (isotonic solution)
Plasmolyzed (hypertonic solution)

Question 29

How do plants become flaccid

Answer 29

If plant cells are surrounded by a more concentrated solution, water moves out from the cells by osmosis

-vacuole and cytoplasm shrivel and the cell membrane moves away from the cell wall.

-the more concentrated solution fills the gaps between the cell membrane and the cell wall.
Cell loses turgor

Question 30

Plasmolysis

Answer 30

The loss of water and the movement of the cell membrane away from the cell wall
-causes plants to wilt

Question 31

Examples of food preservation using osmosis

Answer 31

Fish and meat soaked in a salt solution
Fruit is preserved in jams by using a high sugar concentration

Question 32

Osmosis and food preservation

Answer 32

-bacteria and fungi are the most common cause of food spoilage.
Their cells are enclosed by a membrane

-if food is placed in a salty or sugary solution
Any bacteria or fungi present will lose water from their cells, shrivel and die