2.4.5-2.4.9~osmosis

Question 1

what are all cells surrounded by

Answer 1

a cell membrane which is partially permeable

Question 2

how can water move in and out of cells

Answer 2

osmosis

Question 3

osmosis definition

Answer 3

net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane

Question 4

water concentration gradient

Answer 4

water moves down the concentration gradient

Question 5

water potential of pure water at atmospheric pressure

Answer 5

0KPa

Question 5

partially permeable

Answer 5

allows small molecules through but not larger molecules

Question 5

water potential

Answer 5

tendency of water to move out of a solution

Question 6

water potential of solution

Answer 6

lower than 0KPa (negative value)

Question 7

diffusion of plant cell in pure water/dilute solution

Answer 7

water will enter the plant cell through its partially permeable cell surface membrane by osmosis, as the pure water/dilute solution has a higher water potential than the plant cell

Question 8

volume of plant cell as water enters vacuole

Answer 8

increases

Question 9

pressure in plant cell

Answer 9

expanding protoplast pushes against cell wall and pressure builds

Question 10

what prevents cell from bursting

Answer 10

inelastic cell wall

Question 11

cell wall effect on pressure

Answer 11

pressure created by cell wall stops too much water from entering and prevents cell from bursting

Question 12

turgid

Answer 12

when a plant cell is fully inflated with water and has become rigid and firm

Question 13

importance of turgidity

Answer 13

turgidity is important as effect of all the cells in a plat being firms is to provide support and strength for the plant which makes it stand upright with its leaves held out to catch sunlight

Question 14

if plants do not receive enough water

Answer 14

cells cannot remain turgid and plant wilts

Question 15

severity of effects on osmosis in animal cells

Answer 15

more severe than in plant cells as don not have a cell wall

Question 16

animal cells if water leaves by osmosis

Answer 16

water will leave the cell through its partially permeable cell surface membrane by osmosis and the cell will shrink and shrivel up

Question 17

environment where water leaves cell by osmosis

Answer 17

hypertonic

Question 18

what is a hypertonic environment

Answer 18

solution outside of the cell has a higher solute concentration than inside the cell

Question 19

what happens if you put an animal cell in water or dilute solution (higher water potential than the cell)

Answer 19

water enters the cell through the partially permeable cell surface membrane by osmosis, the cell will continue to gain water by osmosis until cell membrane is too far stretched and the cell bursts

Question 20

cytolysis

Answer 20

water gained by osmosis causes the cell membrane to be stretched so far and the cell bursts

Question 21

why does an animal cell bust

Answer 21

no cell wall to withstand the increased pressure

Question 22

environment where cell gains water due to osmosis

Answer 22

hypotonic

Question 23

what is a hypotonic environment

Answer 23

the solution outside the cell has a lower solute concentration than the inside if the cell

Question 24

isotonic environment

Answer 24

solution outside of the cell has the same solute concentration as the inside of the cell

Question 25

what happens if animal cell is in isotonic environment

Answer 25

the movement of water molecules into and out of the cell occurs at the same rate and there is no change to the cells –> no net movement if water

Question 26

similarity of cell wall in animal and plant cell

Answer 26

-present composed of a phosopholipid bilayer
-partially permeable

Question 27

difference of cell wall in animal and plant cell

Answer 27

-plant cell is fully composed of cellulose and is fully permeable
-animal cell has no cell wall

Question 28

similarity of osmosis of water into and out of the cell for animal and plant cells

Answer 28

can occur

Question 29

plant cell placed in solution with lower water potential

Answer 29

-water leaves cell through partially permeable cell surface membrane by osmosis
-volume of the cell decreases
-protoplast shrinks and pulls away from cell wall
-cell is plasmolysed

Question 30

animal cell placed in solution with lower water potential

Answer 30

-water leaves cell through partially permeable cell surface membrane by osmosis
-volume of cell decreases
-cell shrinks and shrivels up

Question 31

plant cell placed in solution with higher water potential

Answer 31

-water enters cell through partially permeable cell surface membrane by osmosis
-volume of cell increases
-protoplast expands and pushes against cell wall
-cell wall withstands increased pressure created
-pressure increases until cell is turgid
-cell is fully inflated with water and no more can enter

Question 32

animal cell placed in solution with higher water potential

Answer 32

-water enters cell through partially permable cell surface membrane by osmosis
-volume of cell increases
-no cell wall to withstand increased pressure created
-cell membrane eventually stretched too far and cell bursts

Question 33

how is it possible to investigate water potential

Answer 33

immersing plant tissue in solutions of different water potentials and then using the results to estimate water potential of the plant tissue itself

Question 34

most common osmosis practical to investigate water potential

Answer 34

potato cylinders in a range of solutions with different water potentials (at lease 5 different concentrations usually required)

Question 35

required practical 3 - investigating water potential method

Answer 35

-cut the required number of potatoes ensuring they are all cut to the same length
-blot potatoes dry to remove excess moisture
-record initial mass of potato and record
-leave in solution of set length of time (30mins) in a water bath (30 degrees)
-remove and blot dry to remove excess liquid
-measure and record the length and mass of each potato

Question 36

what analysis is used in investigating water potential practical

Answer 36

percentage change in mass for each potato cylinder

Question 37

positive percentage change in mass

Answer 37

potato has gained water by osmosis so solution has a higher water potential than the potato

Question 38

potato cells when positive percentage change in mass

Answer 38

cells are turgid as water exerts turgor pressure on the cell walls

Question 39

negative percentage change in mass

Answer 39

solution had a lower water potential than the potato so water molecules will move out of the potato cells by osmosis

Question 40

negative percentage change in mass effect on cells

Answer 40

cells are flaccid and may be plasmolysed (cell membrane is pulled away from cell wall)

Question 41

no percentage change in mass

Answer 41

no net movement of water in or out of the potato cells as the solution has same water potential to the cytoplasm inside the potato cells–> so no concentration gradient

Question 42

how do you identify the concentration of sucrose solution from a graph

Answer 42

the point at which the line of best fit crosses the x-axis

Question 43

what does plotting data allow you to see

Answer 43

relationship between two variables

Question 44

what is qualitative data

Answer 44

non-numerical data

Question 45

what is discrete data

Answer 45

numerical data that can only take certain values

Question 46

what is continuous data

Answer 46

numerical data that can take any value in a range

Question 47

type of graph for qualitative and discrete data

Answer 47

bar charts or pie charts

Question 48

type of graph most suitable for continuous data

Answer 48

line graphs or scatter graphs

Question 49

axis independent variable be plotted on graph

Answer 49

x

Question 50

axis dependent variable should be plotted

Answer 50

y