| Date | May 2017 | Marks available | 2 | Reference code | 17M.3.SL.TZ2.2 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | State | Question number | 2 | Adapted from | N/A |
Question
Keratin is a protein found in hair, nails, wool, horns and feathers. The graphs show the relative keratinase activity obtained in experiments into keratin digestion at different pH values and different temperatures.
Determine the optimum pH and temperature of keratinase.
Suggest two changes occurring in the reaction vessel that could be used to indicate keratinase activity.
State two conditions that should be kept constant in both experiments.
Markscheme
pH=8 AND temperature=46 °C
Both needed.
Accept answers in the range of 7.8 to 8.5 pH and 44 to 48 °C .
Units required.
a. the amount of keratin measured OWTTE
OR
decrease in keratin mass
OR
size of keratin containing object
b. the increase in peptides/amino acids/product
c. changes in colour/absorbance/smell
a. amount/concentration of enzyme
b. amount/concentration of keratin/substrate
c. amount of buffer
d. time/duration of experiment
