Spm Biology 2006 K3

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Answer all.questions. I

A group of students carried out an experiment to study the effect of the concentration of albumen 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 the cloudiness of the albumen suspension is shown in Diagram 1.2. The whole experiment in Diagram 1.1 was repeated using different concentrations of albumen suspension. .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

r63 L-

Percentage concentration of albumen suspension

Observation Beginningof experiment

End of experirnent

fime taken / minutes

LOTo

10ml albumen suspension + 1 ml pepsin 17o

n LSVo

10ml albumen suspension + 1 ml pepsin 17o

@ e

20Vo 10 ml albumen suspension + 1 ml pepsin 17o

@ w

Table 1.1 (a) (i) Based on Table 1'1, state two observations on the relationship behreen the quantity of albumen and time. II

1.

[3 marks] t65

(ii) grrt" the inference which corresponds to the observation in (axi). 1"

2.

[3 marks] (b) Using the information provided in Table 1.1, completeTable the time taken - r.2byrecording -'- vJ !vv! ' forthealbumensuspensiontoturnclear. Percentage concentration of 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 t3 marksl r 67

t69

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

[3 marks] (fl

.Basedon 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 of albumen suspension and pepsin urrry*" used are as shown. The experiment is left for one'hour.

Thermometer

Boilingtube

20 ml albumen suspension 20% .+ 1 ml boiled enzyme Waterbath 3Z "C

Diagram 1.8 P, Q, R and S are four possible observations after one hour. choose one correct observati-_and explainyour choice.

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I!U a

R

S

13marksl 173

2

A housewife made fruit pickles using unripe mango. During the preparation, she placed the mango 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 their sizes increased. But when they were placed in the sugar solution, the slices becJ-e sdft and shrunken. Based on the above situation, plan a laboratory experiment to determine the concentration of sucrose which is isotonic to the cell sap of the mango. . The planning ofyour experiment must include the following aspects: o Problem statement o Aim of investigation o Hypothesis ? Variables o List of apparatus and materials o Tbchnique used o Experiment procedure or method o PreBentation of data o conclusion

'\--, IL7rnarksr

t

175

Paper 3 1

(a) (r)

1.

The higher the percentage coneentration of albumen suspension, the more time

(it is needed to change into colourless pepsin of Rate suspension. 2. The lower'the percentage Concentratign' reaction of albumen suspension, the less time is needed to change into colourless suspension. 1.6 of enzymatic reaction (ii) 1. The rate increases with the increase in substrate concentration. 1.5 2. The rate of enzymatic reaction decreases substance decrease in the with concentration. L.4 (b) LO%-7 minutes 15%- 10 minutes 1.3 2lo/o- 13 minutes (c) (r) Variables

Method to handle the variable

Manipulated variable Concentration of albumen suspension

Use differeit concentration of Concentration of albumen suspension' albumen suspension.

10

Time taken for the digestion of albumen.

Albumen suspension becomes colourless.

Controlled variable Enzyme concentration temperature and Ptl *"dt"*"f

1% pepsin, 1 ml of Pepsin, 37'C waterbath, volume of albumen suspension= 10 ml

.

Material

Apparatus

Manipulated

Syringe

Albumen suspension

Responding

Stopwatch

Pepsin

Controlled

T?rermometer

Waterbath

(d) (e)

substrate.

Problem statement: How is the concentration of an external solution which is isotonic to the cell sap ofplant tissues determined?

(ir) Variables

15

(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

Responding variable

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.

The rate of enzymatic reaction increases with the iricrease in substances concenttation (r)

Percentage concentration of albumen

t0o/o

15o/o

20%

fime/min

7

10

13

Rate of enzyme reaction as percentage of albumel converted Perrnin

10

15 10

20 13 = 1.54

n

= 1 .4 3

= 1.50

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 sucrosesolution. Apparatus: Razor blade or shaip scalpel, petri-fishes, forceps, a ruler, 50 ml beaker, an electronic scale, tissue paper'

228

Technique used: Immersed the mango slices in solutions of different concentration. 3.

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 water Petri dish B: 0.1M sucrosesolution Petri dish C:0.2M sucrosesolution Petri dish D: 0.3M sucrose solution

4. 5.

6.

Petri dish E: 0.4M sucrosesolution Petri dish F: 0.5M sucrosesolution . Petri dish G: 0.6M sucrosesolution Each mango slice is wiped dry with some tissue papers. The mass of each slice is measured and recorded. The mango slices must be covered in the solution. Afber soaking for an hour, each slice is removed from its respective petri dish and wiped dry. The mass of each slice is measured again and recorded. The results are recordedin a table.

Presentation ofdata: Mass of mango slice Solution

Petri dish

(s)

Initial mass

Final mass

Different in

% different

length

inlength

Texture appearanoe

Distilled water

A

Firm

0.1 m sucrosesolution

B

Firm

0.2 m sucrosesolution

C

Firm

0.3 m sucrosesolution

D

Firm

0.4 m sucrosesolution

E

Firm

0.5 m sucrosesolution

F

Soft

0.6 m sucrosesolution

G

Soft

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

Paper 2 SectionA 1' (a) (')

(it

Difference in mass (%)

Skin Tbansporting oxygen Regulating body temperature Eliminating urea

Concentration of sucrose solution

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

Converting excessglucoseto glycogen As a protective layer (b) X: Becauseskinconsists ofvarious types oftissues such as connective tissue; muscle tissue; combjned ' together to perform specific functions. Erector muscle: Because erector muscle consists of specialised long cells called muscle fibres .