Think about the following statements carefully. Are they true or false? Check the answers at the back of thebook to get rid of any misconceptions.

1 Active transport is the pumping of mineral salts into the root hairs down a concentration gradient.

2 Water molecules in the hypertonic solution diffuse across the membrane against the concentrationgradient.

3 ln a hypotonic solution, plant cells undergo haemolysis.

4 A plasmolysed cell cannot become turgid again when placed in distilled water.

5 Plants with excess fertiliser will not wilt.

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PAPER 1 Multiple Choice Auestions

lnstruction: Answer al! questions. For each questionthere are four possible answers, A, B, C and D.

Choose the one you consider correct and record yourchoice in the bracket.

1 Which of the following statements is not trueabout diffusion?

A Diffusion is a physical process.B Diffusion occurs if there is a concentration

gradient.C Diffusion involves the movement of sodium

ions from the soil of a pond into freshwaterplants against a concentration gradient.

D Diffusion can occur in the absence of a semi-permeable membrane. ( )

2 Which of the following are true about osmosis?

I Movement of solvent moleculesll Occurs in both living and non-living thingslll lnvolves a semi-permeable membranelV Requires chemical energy

A I and lll only B ll and tV ontyC l, ll and lll only D ll, lll and tV onty

()

3 The diagram given below shows the set ofapparatus used in an experiment. After an hour,the Visking tubing which contains solution Z isturgid and its size has increased, while theVisking tubing which contains solutionY isflaccid.

solution X

solution Y

solution Z

What are solutions X,Y and Z?

A

B

c

D

10% sucrosesolution

25olo sucrosesolution

Water

10olo sucrosesolution

25% sucrosesolution

10% sucrosesolution

25% sucrosesolution

Water

Water

Water

10% sucrosesolution

25% sucrosesolution

29

Review Exerci se 2

Solution X Sotution Y Solution Z

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4 An experiment is carried out to study the effectof osmosis on red blood cells using the liquidsbelow.

water 207" SuCrOSe

solution

A

What happens when a drop of blood is addedto test tube A?

A Red blood cells undergo haemolysis.B Red blood cells undergo crenation.C Red blood cells look normal.D Red blood cells agglutinate.

5 The diagram given below shows four plant cellsthat have been placed in solutions B O, R and Srespectively for 30 minutes.

soution P soution O

soution R soution S

Which of the following shows the ascendingorder of the concentration of the solutions?

Hypeftonic lsotonic I Hypotonic

Hypotonic lsotonic , Hypertonic

A

B

cD

B

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7 The table below shows the results of a study onthe concentration of cell sap in a particularspecies of seaweed compared with theconcentration of seawater around it.

Sodiyl. Potassium

What processes must occur to enable theseaweed to obtain the sodium and potassiumions?

A Active transport

B Diffusion

C Osmosis

D Active transport

Osmosis

8 The diagram given below shows the result ofan experiment.The level in the glass tube hasrisen to level X after three hours.

glass tube

initial level ol solution

semi-permeable tubing

0.2 mol/dm3 sucrose solution

lf a student wishes to lower the level of thesolution so that it is below level X, whatchanges must the student make to theappa ratus?

A Use 0.2 mol/dm3 of sucrose solution in thebeaker

B Use 0.4 mol/dm3 of sucrose solution in thebeaker

C Use a smaller tubingD Fill tubing with water (

lsotonic Hypotonic Hypertonic

Hypotonic Hypertonic lsotonic

Active transpoft

Active transpoft

Diffusion

X

A BR,S,OC R,S,BO oB

B O,PD S,R,

R,S

6 Three types of cells, red blood cells, cheek cellsand plant cells, were placed in solutions O, R

and S respectively. After20 minutes, slides for each type of cell wereprepared and observed under a microscope.The diagram given shows the conditions of thethree types of cells.

red blood cell cheek cell plant cell

solution Q solution R solution S

Which of the following is true about theconcentrations of solutions O, R and Scompared with the initial concentration of the

solution in the cell?

ofsap in seaweed (mg

ion/dm3)

Potassium ionsSodium ions

30

)

lon Concentrationol seawater

tmg ion/dm3l

237 486

15

( )

XOffi )

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9 The diagram given below shows an experimentto study the movement of substances across amembrane by using a Visking tubing.

level in

capillary tu

beaker

distilled water

Visking tubing 207" sucrosesolution

Which of the following statements is true?

A The level of the solution in the beakerincreases.

B Sucrose molecules diffuse out of the Viskingtubing.

C Water molecules diffuse out of the Viskingtubing.

D The Visking tubing will expand. ( )

10 A few potato strips of the same length areprepared and placed in distilled water,0.4 mol/dm3 sucrose solution and3.0 mol/dm3 sucrose solution respectively. After20 minutes, the length of each strip is measuredand the results recorded.

Distilled water

0.4 mol/dm3 surcosesolution

3.0 mol/dm3 surcosesolution

10 11.4

10 IU

8.6

What conclusion can be formed from theresults of the above experiment?

A Distilled water is hypertonic, 0.4 mol/dm3sucrose solution is hypotonic and 3.0 mol/dm3sucrose solution is isotonic to theconcentration of the potato cells.

B Distilled water is hypotonic, 0.4 mol/dm3sucrose solution is isotonic and 3.0 mol/dm3sucrose solution is hypertonic to theconcentration of the potato cells.

C Distilled water is hypertonic, 0.4 mol/dm3sucrose solution is isotonic and 3.0 mol/dm3sucrose solution is hypotonic to theconcentration of the potato cells.

D Distilled water is hypotonic, 0.4 mol/dm3sucrose solution is hypertonic and3.0 mol/dm3 sucrose solution is isotonic tothe concentration of the potato cells.

()

11 The diagram given below shows an experimentto study the movement of substances acrossthe plasma membrane.

capillary level 1

concentrated level 2

sucrosesolution semi-permeable

membrane

What happens after four hours?

I The level at 1 increases.ll The level at 2 increases.lll Water molecules diffuse inwards through the

membrane.lV Sucrose molecules diffuse outwards through

the membrane.

A I and lll onlyB I and lV onlyC ll and lll onlyD ll and lV only

12 The diagram given below shows two types ofsucrose solutions being separated by a semi-permeable membrane in a U-tube.

B

37o SUCTOSe

solution1 7o sucrosesolution

Key: semi-permeableo Water molecule membraneo Sucrose molecule

What happens when equilibrium is achieved?

I The solvent molecules diffuse from 3Yo

sucrose solution to 1% sucrose solution.ll Water molecules move at equal rate on both

sides of the membrane.lll The osmotic pressure of the sucrose solution

in both A and B are the same.lV The level of the sucrose solution at A is higher

than the level of sucrose solution at B.

A I and lV onlyB l, ll and lll onlyC ll, lll and lV onlyD l, ll, lll and lV

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Final lengthlnitial lengthSolution

Length of potato strips (cml

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13 Samples of potato were placed in sucrosesolutions of different concentrations. Anychanges in the masses of the samples werenoted. Which graph shows the results of thisexperiment?

A Length ol potatostrip (mm)

Time

C Length of potatostrip (mm)

Tima

D Length of potatostrip (mm)

C Massofsample

Sucroseconcentration

Sucroseconcentration

B Massofsample

D

Sucroseconcentration

50HMass ofsample

15 The diagram given below shows an experimentwhich was used to investigate osmosis in potatotissue.

Tim€

skin

(v) 80% sucrosesolution (V)

Time ( )

()

Sucroseconcentration

() waterfresh potato

14 A student placed a 50 mm strip of potato ineach of the following solutions.

The length of each strip was measured atregular intervals and the results were plotted ona graph.

Which graph shows the correct results?

strong sucrosesolution

Which of the following diagrams showsthe result after 24 hours?

A B

(vi) Distilledwater (W)

Dc

PAPER 2 Structured and Free-response Auestions

Section A Structured Ouestions

1 An experiment is carried out to study the effects of different concentrations of sucrose solutions on

onion cells. Section A of the diagram below shows the treatment of an onion using different solutions.Study the diagram below and answer all the questions.

(i) Distilledwater (R)

epidermal

cell of onion

(iii) 30% sucrosesolution (T)

(iv) Distilledwater (U)

gE g HR S

(a) Draw the cell as observed under the microscope in section B.

(b)(i) What is the difference in structure between the cells in R andT?(ii) Give one reason for the condition of the cell inT.

(c) Describe what happens to the onion cells inT and U.(d) Explain your drawings for the onion cells in V and W.

WUT

i) 8% sucrosesolution (S)

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B Length of potatostrip (mm)

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,,F ,'..*i ,.

<,():

AMassl rofl/samptel -/l' .

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0.30 0.35 0.40

98 80 40

Concentration of salt solution {g/100cm3)

Percentage of red blood cells bursting (o/ol

2 ln an experiment, the percentage of red blood cells which burst in different concentrations of saltsolution is investigated.The results are recorded in the table below.

0.500.45

-10 trEuJ

4I(J

10 _1(a) Draw a graph to show the effects of the different concentrations of salt solution on the percentage of

red blood cells bursting.(b) Based on the graph drawn, state the concentration of salt solution when the number of red blood

cells bursting is equal to the number of red blood cells not bursting.(c) Why do the red blood cells not burst in 0.48 g/100cm3 salt solution?(d) Explain what happens to the red blood cells in 0.50 g/100cm3 salt solution.(e) Why do the onion cells not burst when immersed in distilled water?(f) Explain why a plant will wilt and finally die when too much feftiliser is used.

3 The amoeba is a unicellular organism which can live in fresh water as well as in salt water.The amoebaliving in fresh water has a contractile vacuole used to pump water out of the cell while the amoebaliving in salt water does not have one.

(a) Explain why this is so.(b) How does gas exchange in the amoeba take place under these conditions?

4 An experiment was conducted to study the transport of ions across the cell membrane of an animal cellThe ion concentration inside and outside of the animal cell was measured and recorded in the tablegiven below.

K-

Na-

Mg'-

cl-

130

10

40

10

10

140

10

140

a) (i) Which ions are transported out of the cell by active transport?(ii) Which ions are transported into the cell by active transport?

(b)Explain how you got your answer in (a)

Section B Free-response Ouestions

5 The movement of substances across the plasma membrane of the root hair cells enables the plant toobtain the substances it needs.

(a) Explain how(i) water in the soil enters the roots of the plant.(ii) calcium in the soil enters the roots of the plant.

The concentration of a solution surrounding the cell will influence the function of the cell. Solutions thatare isotonic, hypotonic and hypertonic can affect both plant cells and animal cells.

(b)(i) What is the meaning of isotonic, hypotonic and hypertonic?(ii) Describe the effects of these three solutions on red blood cells.(iii) Describe how red blood cells are prevented from being destroyed in the blood.

Outside the cell

33

lon{mM}

lnside the cell',

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1.00

0.80

0.60

0.40

0.20

0.00 (distilled water)

10

10

10

10

10

10

9.30

9.50

9.70

9.95

10.20

10.60

(a) Name the process that caused the change in the length of the potato strips when they were placed insugar solutions with different concentrations.

(b) Explain why some potato strips showed an increase in length while the others showed a decrease inlength.

(c) The smallest change in the length of the potato strips was recorded when a strip was placed in a

sugar solution of concentration 0.40 mol/dm3. What does this mean?(d) How is the process involved important to plants?

Length ol potato strip (cml

After soakingBefore soaking

34

6 A student cut identical 10 cm-long potato strips and studied how the lengths of the strips changed whensoaked in different concentrations of sugar solutions for 24 hours.The results are given in the tablebelow.

Concentration ol sugar solution(mol/dm3)

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