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The mark scheme for cambridge international examinations international general certificate of secondary education (igcse) biology paper 6 (alternative to practical) for the may/june 2014 series. It provides guidance on how marks should be awarded for each question, including the criteria for accurate answers, use of appropriate terminology, and adherence to the experimental procedure. The mark scheme covers various topics such as enzymes, ph, and the breakdown of fat, and it includes assessment of students' understanding of experimental techniques and data analysis.
What you will learn
Typology: Exams
1 / 4
International General Certificate of Secondary Education
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 should be read in conjunction with the question paper and the Principal Examiner
Report for Teachers.
Cambridge will not enter into discussions about these mark schemes.
Cambridge is publishing the mark schemes for the May/June 2014 series for most IGCSE, GCE
Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.
Page 2
Mark Scheme
Syllabus
Paper
IGCSE – May/June 2014
© Cambridge International Examinations 2014
Mark Scheme
Mark
Guidance
(a)
candidates
have
filled
in
temperatures
(lowest
to
highest) ;times are transferred in correct sequence 0–20 ;colour of indicator recorded correctly from Fig.1.1 in all columns ;
(b)
(i)
lipase works best in alkaline conditions / provides suitable pH forlipase ;
(ii)
idea that both tubes reach the experimental temperature ;
(iii)
fatty acids produced by the breakdown of fat ;(acids) lower pH (causing colour to change) ;
(iv)
stays blue
no colour change ;
enzyme doesn’t react
denatured
(v)
anomalous 21
°C, for 10 min ;
reason: idea that the colour changes are not in theexpected order ;
(c)
2 of:
enzyme concentration ;
same source
concentration of enzyme
lipase used in all
tubes ;
substrate concentration ;
same source of milk
same type of milk
or named type ;
indicator ;
same concentration
volume added
comparison of colour with
chart or meter;
timing length of reaction;
minute intervals precisely using timing device;
Page 4
Mark Scheme
Syllabus
Paper
IGCSE – May/June 2014
© Cambridge International Examinations 2014
(c)
(i)
(xes) – labelled with units and suitable even scale ;
(ize) – occupies at least half the grid ;
(lot) – all points plotted accurately
½ square ;
(ars) – have an equal gap between each component ;
(ii)
22.25 + 0.25 + 2.00 + 2.50 = 27 ;100 – 27 (ecf) = 73 (ecf) ;
(d)
(i)
day 5 ;maximum reducing sugar content ;OR day 4;skin has gone completely yellow;
(ii)
6 times ;
(iii)
the starch has been broken down to (reducing) sugar ;
(iv)
2 features from: colour
taste
smell ;;
max [1]
[Total: 23]