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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 .