unit 3

Question 1

What is diffusion

Answer 1

The spreading out of molecules in a liquid or gas from an area of higher concentration to an area of lower concentration.

Question 2

What happens if there is a higher temperature

Answer 2

Higher kinetic energy causing the particles to move faster

Question 3

How does the particle move

Answer 3

The particles move randomly.

Question 4

Real life example of diffusion

Answer 4

An example of diffusion in gases is water vapour mole diffusing out of a leaf

Question 5

What happens in diffusion

Answer 5

Molecules move down a concentration gradient as a result of their random movement

Question 6

How to calculate concentration

Answer 6

Concentration = mass (g) / volume (dm 3)

M
C. V

Question 7

Factors that affect diffusion

Answer 7

Short distance = faster diffusion (cell membranes are very thin)
Steep / high concentration gradient = the greater the concentration difference faster diffusion happens
large surface area = more molecules can diffuse in or out
Temperature = molecules move faster at high temperatures

Question 8

What is osmosis

Answer 8

Osmosis is the movement of water molecules down a water concentration gradient trough a partially permeable membrane

Question 9

What is partially permeable membrane

Answer 9

Only some molecules can pass through the membrane

Question 10

High water concentration =

Answer 10

Low solute concentration = dilute

Question 11

Low water concentration =

Answer 11

High solute concentration = dilute

Question 12

Key role of osmosis

Answer 12

• controlling guard cells
• uptake of water roots

Question 13

How could you even out the concentration of both side of a membranes

Answer 13

Water will move from the dilute solution with a high water potential to the concentration solution with a low water potential

Question 14

Osmosis (in terms of water potential)

Answer 14

The net movement of water molecules form a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) through a partially permeable membrane

Question 15

Water molecules diffuse down a

Answer 15

Water potential gradient

Question 16

More concentrated solutions have a

Answer 16

Lower water potential

Question 17

What happens to an animal cell when placed in distilled water

Answer 17

Water will diffuse into the cell from an area of high water potential (distilled water) to an area of low water potential (concentrated solution inside the cell). The cell will swell until it bursts

Question 18

What happens to an animal cell when placed in a very concentrated solution?

Answer 18

Osmosis takes place - water will diffuse out of the cell. The cell loses water, the cytoplasm shrinks and the cell gets smaller.

Question 19

Testing for osmosis Dialysis tube mimick cell membrane

Answer 19

water can cross jt but large molecules like salts and sugars can’t

Question 20

What happens to plant cell when placed in distilled water?

Answer 20

Osmosis takes place - water will diffuses into the cell, cytoplasm and vacuole swell and press out against the cell wall. The cell wall withstands this pressure (turgor pressure ) and the cell doesn’t burst.
The cell is turgid

Question 21

What happens to a plant cell when placed in a concentrated solution?

Answer 21

Osmosis takes place - water will diffuses out of the cell, cytoplasm and the vacuole shrink and the turgorg pressure decreases. The cell is flaccid. If the cytoplasm is detached from the cell wall, the cell is said to be plasmolysed.

Question 22

Testing for osmosis in a plant :
Pieces of potatoes are placed into liquids with different concentrations of salts and sugars

Answer 22

Osmosis will take place )
- In distilled water (high water potential) the tissue will swell
- in a concentrated solution (low water potential) the potato tissue will loose water and shrink in size.

Question 23

What is active transport

Answer 23

Active transport is the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration

Question 24

Root hair cells absorbs …

Answer 24

Picks up minerals from the soil. The concentration of minerals is a lot higher in root hair cells than in the surrounding soil solution.

Question 25

What does cells use energy for

Answer 25

To move substances up / against their concentration gradient

Question 26

Why is energy need for a carrier protein

Answer 26

To release molecules on the other side of the membrane. From an area of low concentration to a an of high concentration

Question 27

Why am foe sthat have been dried by leaving them in the sun taste sweeter than fresh mangoes.

Answer 27

Water is lost when frying. The sugars inside remain. Same amount of sugars in a volume of water = higher concentration

Question 28

Explain why water moves out of the mango pieces when they are immersed in a 65% sugar solution

Answer 28

Water moves by osmosis. The 65% sugar solution has a lower water potential (is more concentrated) than the solution in the cell. Water moves down the water potential gradient and out of the cell, through the partially permeable membrane.

Question 29

Suggest why the mangoes need to be left in the sugar solution first 6bh to shield the best results

Answer 29

Osmosis is a random process which takes time

Question 30

Explain why the process works best when the mangoes are sliced into pieces 5 mm thick rather then left whole

Answer 30

Increases surface area across which is issued can happen and reduces the distance water moves to exit = faster process

Question 31

High water potential

Answer 31

An area where there are a lot of water molecules - a dilute solution

Question 32

Low water potential

Answer 32

An area where there are not many water molecules- a concentrated solution

Question 33

Hypertonic

Answer 33

Greater solute concentration

Question 34

Hypotonic

Answer 34

Having a lower osmotic pressure than a particle fluid

Question 35

Isotonic

Answer 35

Two solutions of equal concentrations of solutes and water separated by a semipermeable membrane to allow water to move freely in and out of the cell