Page 173 - SUBSEC October 2017_Neat

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02107032/CAPE/SPEC/KMS 2017

BIOLOGY

UNIT 1 -- PAPER 032
MARK SCHEME

Question 2. UK XS

(a) (i) X-axis correct and properly labelled 1

Y-axis correct and properly labelled 1
Points plotted correctly for salivary amylase 1

Points plotted correctly for arginase 1

Curve smoothly drawn for salivary amylase 1

Curve smoothly drawn for arginase 1

(ii) Optimal pH Arginase 9.5 -- 10.0 pH
1
(Any point in this range -- 1 mark)

Optimal pH Salivary amylase 6.5 -- 7.0 pH
1
(Any point in this range -- 1 mark)

(iii) 7.6 -- 8.4 range
1
(Any point in this range -- 1 mark)

(iv)  pH affect the primary structure of enzymes.
 At pH 7, active site has the correct conformation
shape and substrate -- enzyme complex can form. 3
 At pH 5, conformation of active site is altered --
enzyme substrate complex can no longer form.

3 points -- 3 marks

(b) (i) Graph line A 1

(ii)  Rate of reduction shown in graph line A is higher
than that for graph line B.
 Rate of reduction increases as substrate 3
concentration increases and then levels off.
 Active sites become saturated.

(iii) 4.5 -- 5.5 mols/dm

1 mark for valve within range above 1
1 mark for units 1

Total 18 marks 6 12

Syllabus Objectives: 4.1, 4.2, 4.3, 4.5 - Module 1