eI feog lofC ltll& t hour 3o minutes

Answer all.questions.

I A group of students carried out an experiment to study the effect of the concentration ofalbumen suspension on the rate of reaction ofpepsin enzyme.

Diagram 1.I- shows the method used by the students. The time taken for the change in thecloudiness of the albumen suspension is shown in Diagram 1.2.

The whole experiment in Diagram 1.1 was repeated using different concentrations of albumensuspension.

.Table 1.L shows the results of the experiment.

Thermometer

Boilingtube

10 ml albumen suspension+

1 ml enzyme pepsin 17o

WaterbathST "C

Observation at the beginning of experiment

Diagrarn 1.1

Observation at the end of experiment

Diagram 1.2

L-

r63

Percentageconcentration

of albumensuspension

LOTo

Observation

fime taken / minutesBeginningofexperiment

End ofexperirnent

10 mlalbumen suspension

+1 ml pepsin 17o

LSVo10 ml

albumen suspension+

1 ml pepsin 17o

n

@20Vo

10 mlalbumen suspension

+1 ml pepsin 17o

e

@wTable 1.1

(a) (i) Based on Table 1'1, state two observations on the relationship behreen the quantity ofI Ialbumen and time.

1.

t65[3 marks]

(ii) grrt" the inference which corresponds to the observation in (axi).

1"

2.

[3 marks](b) Using the information provided in Table 1.1, complete Table r.2byrecording the time taken' forthealbumensuspensiontoturnclear. - -'- vJ !vv!

Percentage concentrationof albumen suspension fime taken / minutes

LOVo

ISVo

2OVo

Table 1.2

[3 marksl

(c) (i) Complete Table 1.8 based on this experiment.

Method of handle the variable

Manipulated variable

Respondingvariable

Table 1.3

r67

t3 marksl

t69

(iii) Explain the relationship between the rate of reaction of pepsin and the concentration ofalbumen suspension based on the graph in l(e)(ii). :

20 ml albumen suspension 20%.+

1 ml boiled enzyme

P, Q, R and S areand explainyour

[3 marks](fl .Based on this experiment, what can you deduce about this enzyme?

lB marks)(g) The experiment is repeated using the apparatus set {p as in Diagram 1,8. The quantities ofalbumen suspension and pepsin urrry*" used are as shown.

The experiment is left for one'hour.

Thermometer

Boilingtube

four possiblechoice.

l lt lt-t lU

P

Waterbath 3Z "C

Diagram 1.8

observations after one hour. choose one correct observati-_-

l lI

a

l l!

RU

S

173

13 marksl

2 A housewife made fruit pickles using unripe mango. During the preparation, she placed themango slices in water and later placed them in sugar solution.

When the mango slices were in the water,'ii was found that, the slices, became turgid and theirsizes increased. But when they were placed in the sugar solution, the slices becJ-e sdft andshrunken.

Based on the above situation, plan a laboratory experiment to determine the concentration ofsucrose which is isotonic to the cell sap of the mango. .

The planning ofyour experiment must include the following aspects:o Problem statemento Aim of investigationo Hypothesis? Variableso List of apparatus and materialso Tbchnique usedo Experiment procedure or methodo PreBentation of data

'\--,o conclusion

IL7 rnarksr

t

175

Paper 3

1 (a) (r) 1. The higher the percentage coneentrationof albumen suspension, the more time

is needed to change into colourlesssuspension.

2. The lower'the percentage Concentratign'of albumen suspension, the less time

is needed to change into colourless

suspension.(ii) 1. The rate of enzymatic reaction

increases with the increase in substrateconcentration.

2. The rate of enzymatic reaction decreaseswith the decrease in substanceconcentration.

LO%-7 minutes15% - 10 minutes2lo/o - 13 minutes(r)

The rate of enzymatic reaction increases with the

iricrease in substances concenttation(r)

Concentration ofalbumen suspension

(ii;) The rate of pepsin reaction increases with

the percentage of the concentration ofalbumen

suspension and it reaches a maximum value'

(0 This enzyme, which is pepsin acts on albumen

suspension to change it into clear solution'

The rate of enzyme reaction increases with the

substrate concentration.(g) R. The 1 ml of enzyme used is boiled enzyme, hence

it is denatured/destroyed and cannot act on the

. substrate.

Problem statement:How is the concentration of an external solution which

is isotonic to the cell sap ofplant tissues determined?

Aim of investigation:To determine the concentration of an external solution

which is isotonic to the cell sap of plants.

Hypothesis:When plant cells are immersed in isotonic solution,

there is no nett gain in mass and size.

Manipulated variable:Concentration of sucrose solution.

Responding variable:Mass of strips of mangoes. .

.Controlled variable:Surrounding temperature and time.

Materials:Mango slices, distilled water, 0.1M, 0.2M, 0.3M, 0'4M,

0.5M and 0.6M sucrose solution.

Apparatus:Razor blade or shaip scalpel, petri-fishes, forceps,

a ruler, 50 ml beaker, an electronic scale, tissue paper'

(itRate of pepsinreaction

1.6

1.5

L.4

1.3

(b)

(c)

1510

(d)

(e)

Variables Method to handle the variable

Manipulatedvariable

Concentration of

albumen suspension'

Use differeit concentration of

albumen suspension.

Respondingvariable

Time taken for the

digestion of albumen.

Albumen suspension becomes

colourless.

Controlled variable

Enzyme

concentration

temperature and Ptl

"f *"dt"*-

-

1% pepsin, 1 ml of Pepsin, 37'C

waterbath, volume of albumen

suspension = 10 ml

(ir)

Variables Apparatus Material

Manipulated Syringe Albumensuspension

Responding Stopwatch Pepsin

Controlled T?rermometer Waterbath

Percentage concentrationof albumen

t0o/o 15o/o 20%

fime/min 7 10 13

Rate of enzyme reactionas percentage of albumelconverted Perrnin

10n

=1.43

1510

= 1.50

2013

= 1.54

228

Technique used:Immersed the mango slices in solutions of differentconcentration.

Proeedure:1. Seven petri dishes are prepared and labelledA, B,

C, D, E, F and G.2. Each beaker is filled with the following solutions

respectively:Petri dishA: Distilled waterPetri dish B: 0.1M sucrose solutionPetri dish C:0.2M sucrose solutionPetri dish D: 0.3M sucrose solution

Petri dish E: 0.4M sucrose solutionPetri dish F: 0.5M sucrose solution .

Petri dish G: 0.6M sucrose solution3. Each mango slice is wiped dry with some tissue

papers. The mass of each slice is measured andrecorded.

4. The mango slices must be covered in the solution.5. Afber soaking for an hour, each slice is removed

from its respective petri dish and wiped dry. Themass of each slice is measured again and recorded.

6. The results are recordedin a table.

Presentation ofdata:

Solution Petri

dish

Mass of mango slice(s) Different in

length

% different

inlength

TextureappearanoeInitial

massFinalmass

Distilled water A Firm

0.1 m sucrose solution B Firm

0.2 m sucrose solution C Firm

0.3 m sucrose solution D Firm

0.4 m sucrose solution E Firm

0.5 m sucrose solution F Soft

0.6 m sucrose solution G Soft

A graph of the percentage difference in mass againstthe concentration of sucrose solution is drawn.

Difference in mass (%)

Skin

Tbansporting oxygen

Regulating body temperature

Eliminating urea

Converting excess glucose to glycogen

As a protective layer

Paper 2SectionA1' (a) (')

(it

Concentration ofsucrose solution

Conclusion:Based on the graph above, the concentration ofthe cellsap of mango slice is yM.

(b) X: Because skinconsists ofvarious types oftissuessuch as connective tissue; muscle tissue; combjned

' together to perform specific functions.Erector muscle: Because erector muscle consists ofspecialised long cells called muscle fibres .