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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS
GCE Ordinary Level

MARK SCHEME for the October/November 2011 question paper
for the guidance of teachers

5090 BIOLOGY
5090/32

Paper 3 (Practical Test), maximum raw mark 40

This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of
the examination. It shows the basis on which Examiners were instructed to award marks. It does not
indicate the details of the discussions that took place at an Examiners’ meeting before marking began,
which would have considered the acceptability of alternative answers.
Mark schemes must be read in conjunction with the question papers and the report on the
examination.

• Cambridge will not enter into discussions or correspondence in connection with these mark schemes.

Cambridge is publishing the mark schemes for the October/November 2011 question papers for most
IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level
syllabuses.

Page 2
1

Mark Scheme: Teachers’ version
GCE O LEVEL – October/November 2011

Syllabus
5090

(a) (i) drawing marks;
at least 7 cm good shape, (ridged) entire outline of transverse section;
realistic vascular bundles;
stained areas shown;
labels:
vascular bundles / xylem;
stained areas indicated;
epidermis / thickened tissue; R – epicarp
(ii) shown where measured;
measurements to 1 mm (0.1 cm); (units/decimals given at least once)
drawing size over specimen equivalent;
magnification suitably expressed;
(b) (i) simple diagram of vertical section (R – transverse section);
simple diagram of streak of stain down tissue (v.b.);
ref spread down tissue;
ref staining of other (thickened) tissue at end of specimen;
(ii) uniform (all parts) in potato – regional (mainly v.b., xylem) in celery;
more heavily stained in potato, less heavily stained in celery /
turns black in potato, brown in celery;

Paper
32
[3]

[max 2]

[4]

[max 3]

[2]

(c) starch turns black with iodine;
uniform/ all over/ widely spaced in potato tissue;
ref to storage (tissue/organ);
xylem / vascular/ conducting / tubular tissue in celery; (R – phloem as conducting tissue)
no/less starch in celery (or reverse more starch in potato);
ref staining of walls /xylem
ref to lignified tissue;
[max 6]
[Total: 20]
2

(a) (i) preparation – cut/crush /chop (on tile);
dissolve /shake in ethanol;
add water / to water;
cloudy /chalky/ white emulsion if fat present; R – precipitate
remains clear/colourless / no change if none;

[max 4]

(ii) preparation – cut/crush/chop (on tile)
add Biuret reagent;
mauve /purple /lilac / violet if protein present; R – precipitate
remains blue/no colour change if none;

[4]

© University of Cambridge International Examinations 2011

Page 3

Mark Scheme: Teachers’ version
GCE O LEVEL – October/November 2011

(b)

Syllabus
5090

Paper
32

Table 2.1
fats
Observation

Conclusion

proteins

W1

W2

W1

W2

stays clear /
faintly cloudy

goes cloudy

faintly mauve

goes mauve

no fat /
small amount

fat present

small amount
present

protein present

Marks for Table
note that alternatives for colour observations are given in (a)(i) and (ii).
column 1 (I mark if consistent)
column 2 (2 marks to allow clear terminology for fats)
column 3 (1 mark if consistent and to allow positive results for proteins)
column 4 (2 marks to allow clear terminology for proteins)
(c) suitable named specimens e.g. W1/W2/ food rich in fats, carbohydrates;
measured mass (of substrate) ;
measured volume (of water);
use of forceps /needle and ignited/burned;
used to heat water (in tt);
measure initial and subsequent temperature;
note temp. increase;
more energy release;
repeat the procedure /compare with another specimen;
OVP – re-ignition/ complete combustion /replication and taking mean values

[6]

[max 6]
[Total: 20]

© University of Cambridge International Examinations 2011


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