Biology · May / June 2024 · Paper 41 · Question 4

any three from:

row 1 – lactase breaks down lactose into glucose (and galactose in milk) ; row 2 – lactose-free milk has already been treated with lactase (so glucose is already present) ;

row 3 – sucrose, is not broken down / does not contain lactose / AW ; lactase is specific for breakdown of lactose / AW

OR

lactose only fits into active site of, lactase / enzyme ;

any four from:

1

at optimum temperature maximum enzyme activity or rate of reaction OR outside the optimum / when cold / when hot, reduced, enzyme

activity / rate of reaction ;

2

at optimum temperature maximum, successful collisions / enzyme- substrate complexes (ESCs)

OR

outside the optimum / when cold / when hot, fewer, successful

collisions / enzyme-substrate complexes (ESCs) ;

3

as temperature increases kinetic energy increases / ora ;

4

ref to denaturation at, high temperatures / temperatures above optimum ; 5

(so) shape of active site changes ;

6

(so) lactase is no longer complementary to the lactose ;

7

AVP ; e.g. ref. to temperature as a standardised variable

any two from:

milk contains, calcium ;

calcium / vitamin D, required for, healthy / strong / AW, teeth / bones ; (calcium / vitamin D) prevent, rickets / any symptom of rickets ;

AVP ;

ref. to all nutrients / all food groups / AW ;

idea of nutrients in the, correct / appropriate / healthy, proportions / amounts OR

to provide suitable amount of energy for, level of activity / (stated) lifestyle(s) ;