B2.1 Osmosis

Question 1

Define Osmosis

Answer 1

The diffusion of water from a dilute solution to a more concentrated solution through a selectively permeable membrane

Question 2

What can only pass through the membrane?

Answer 2

Water

Question 3

What happens to cells in an isotonic solution?

Answer 3

Nothing

Question 4

What happens to cells when put into a hypotonic solution and how will they appear?

Answer 4

They become turgid - the cells swell and burst

Question 5

What happens to a cell when placed into a hypertonic solution and how will it appear?

Answer 5

It becomes plasmolysed - the cells shrivel and the cytoplasm shrinks from the cell wall

Question 6

Plants use water for support, what does it maintain and stop?

Answer 6

Maintain turgor and stop wilting

Question 7

Plants use water for photosynthesis, why is this?

Answer 7

Water is a raw material needed for photosynthesis

Question 8

Plants use water for transport, why is this?

Answer 8

Solvent is needed to transport dissolved substances

Question 9

Plants use water for transpiration, why is this?

Answer 9

Water is needed to drive transpirtation

Question 10

What is transpiration?

Answer 10

The evaporation of water from mesophyll cells followed by diffusion through airspaces and stomata

Question 11

List 2 factors that affect the transpiration pathway in root hair cells

Answer 11

Large surface area
No chloroplasts as it is underground

Question 12

In the transpiration pathway the stem is used for transport and support, how is this achieved?

Answer 12

Water transported in the xylem

Dissolved sugars transported in the phloem

Question 13

In the transpiration pathway, the leaf is used for photosynthesis and transpiration, how is this achieved?

Answer 13

Water diffuses out through the stomata on the underside of a leaf

Question 14

Light intensity increases transpiration, why?

Answer 14

Increased rate of photosynthesis, open stomata allow Co2 in, water can diffuse out.

Question 15

Temperature increases the rate of transpiration, why?

Answer 15

Increased evaporation

Question 16

Wind increases the rate of transpiration, how?

Answer 16

Increase in evaporation due to the concentration gradient being maintained as wind blows moist air away.

Question 17

Humidity decreases the rate of transpiration, how?

Answer 17

There is a decrease in the concentration gradient for moisture when the humidity increases meaning there is less transpiration.

Question 18

What is the role of the cell wall in osmosis?

Answer 18

To limit the entry of water

Question 19

What happens when a potato is placed into a solution of 0% sucrose?

Answer 19

Water moves into the potato and it becomes turgid, causing the cells to swell

Question 20

What happens when a potato cell is placed into a 34% sucrose solution?

Answer 20

Water moves out of the potato and becomes plasmolysed, meaning the cells shrivel and the cytoplasm shrinks from the cell wall

Question 21

Why would blood cells burst when put into a hypotonic solution?

Answer 21

Lack of cell wall